Coexistence of Grant-Based and Grant-Free Uplink Transmissions in a Channel

ABSTRACT

Aspects of this disclosure mitigate interference in a time division duplexed frame by altering a transmission parameter of grant-based uplink transmissions upon determining that a portion of the grant-based transmission will coincide with the retransmission of a detected grant-free uplink transmission. In particular, a base station may determine that a grant-free retransmission is to occur over resources scheduled to carry a grant-based transmission, and then send a signal instructing a UE to delay, or puncture a portion, of the grant-based transmission. This may mitigate interference between the grant-based transmission and the grant-free transmission.

This application is a continuation of PCT Application No.PCT/CN2017/091274, filed on Jun. 30, 2017, which claims priority to U.S.Non-Provisional application Ser. No. 15/223,690, filed on Jul. 29, 2016entitled “System and Method for Retransmission of Grant-Free Traffic”and U.S. Provisional Application No. 62/416,536, filed on Nov. 2, 2016and entitled “Coexistence of Grant-Based and Grant-Free UplinkTransmissions in a Subframe,” all of which are incorporated herein byreference as if reproduced in their entirety.

TECHNICAL FIELD

The present invention relates generally to a method and device forcoding, and, in particular embodiments, to techniques for supporting thecoexistence of grant-based and grant-free uplink transmissions in achannel.

BACKGROUND

Various multiple access schemes can be used to allow multiple userequipments (UEs) to access shared resources of an uplink channel. Onetype of access scheme (referred to herein as “grant-based access”)requires UEs to request that channel resources be scheduled to carry anuplink data transmission prior to performing the uplink datatransmission. Another type of access scheme (referred to as “grant-freeaccess”) allows UEs to perform uplink data transmissions over one ormore uplink resources without requesting that those resources bescheduled to carry the uplink data transmission. In conventionalnetworks, data channel resources are exclusively allocated for eithergrant-based access transmissions or grant-free access transmission sothat grant-based and grant-free uplink transmissions do not interferewith one another.

SUMMARY

Technical advantages are generally achieved, by embodiments of thisdisclosure which describe techniques for supporting the coexistence ofgrant-based and grant-free uplink transmissions in a channel.

Technical advantages are generally achieved, by embodiments of thisdisclosure which describe techniques for supporting the coexistence ofgrant-based and grant-free uplink transmissions in a channel.

In accordance with an embodiment, a method for mitigating interferenceis provided. In this example, the method includes detecting a grant-freeuplink transmission over a first uplink resource, and determining that aretransmission of the grant-free uplink transmission will occur over asecond uplink resource. The second uplink resource was previouslyscheduled to carry a grant-based uplink transmission from a userequipment (UE). The method further includes transmitting a signal over adownlink resource that instructs the UE to adjust a transmissionparameter of the grant-based uplink transmission. An apparatus forperforming this method is also provided.

In accordance with another embodiment, a method for reconfiguringgrant-free resources is provided. In this example, the method includesscheduling a first uplink resource to carry a grant-based uplinktransmission of a first user equipment (UE). The first uplink resourceis included in an initial set of uplink resources available forgrant-free uplink transmissions. The method further includesbroadcasting a control message that updates the set of uplink resourcesfor grant-free uplink transmissions. The updated set of uplink resourcesexcludes the first uplink resource. An apparatus for performing thismethod is also provided.

In accordance with yet another embodiment, a method for mitigatinginterference in a subframe is provided. In this example, the methodincludes receiving a scheduling instruction indicating that uplinkresources are scheduled to carry a grant-based uplink transmission ofthe first UE, monitoring one or more downlink resources outside adownlink control channel associated with the first UE for an indicationthat a retransmission of a grant-free uplink transmission is to occurover a subset of the uplink resources scheduled to carry the grant-baseduplink transmission of the first UE, and puncturing a portion of thegrant-based uplink transmission corresponding to the subset of uplinkresources upon detecting the indication that the grant-free uplinktransmission is to occur over the subset of uplink resources. Anapparatus for performing this method is also provided.

In accordance with yet another embodiment, another method for mitigatinginterference in a subframe is provided. In this example, the methodcomprises determining that a retransmission of a grant-free uplinktransmission will occur over a subset of uplink resources scheduled tocarry a grant-based uplink transmission of a first user equipment (UE),and transmitting an indication prompting the first UE to puncture aportion of the grant-based uplink transmission that corresponds to thesubset of uplink resources over which the retransmission of thegrant-free transmission will occur. An apparatus for performing thismethod is also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram of an embodiment wireless communications network;

FIG. 2 is a diagram of a TDD subframe that enables the coexistence ofgrant-based and grant-free uplink transmissions over the same uplinkresources;

FIGS. 3A and 3B are graphs of transmit power levels for a grant-baseduplink transmission that coincides with a grant-free uplinkretransmission;

FIG. 4 is a flowchart of an embodiment method for mitigatinginterference between grant-based uplink transmissions and grant-freeuplink retransmissions;

FIG. 5 is a diagram of a subframe during which a set of resources forcarrying grant-free uplink transmissions is reconfigured;

FIG. 6 is a flowchart of an embodiment method for mitigatinginterference between grant-based uplink transmissions and grant-freeuplink transmissions;

FIG. 7 is a diagram of a set of resources scheduled to carry agrant-based uplink transmission of a UE ;

FIG. 8 is a diagram of an embodiment channel structure method formitigating interference between grant-based uplink transmissions andgrant-free uplink transmissions;

FIG. 7 is a diagram of a set of resources scheduled to carry agrant-based uplink transmission of a UE ;

FIG. 8 is a diagram of an embodiment frame format for dynamicallynotifying a UE that a retransmission of a grant-free uplink transmissionwill occur over resources scheduled to carry a grant-based uplinktransmission of the UE;

FIG. 9 is a diagram of another embodiment frame format for dynamicallynotifying a UE that a retransmission of a grant-free uplink transmissionwill occur over resources scheduled to carry a grant-based uplinktransmission of the UE;

FIG. 10 is a flowchart of an embodiment method for puncturing agrant-based uplink transmission to mitigate interference between thegrant-based uplink transmission and a grant-free uplink transmission;

FIG. 11 is a flowchart of an embodiment method 1100 for dynamicallynotifying a UE that a retransmission of a grant-free uplink transmissionwill occur over resources scheduled to carry a grant-based uplinktransmission of the UE;

FIG. 12 is a diagram of an embodiment uplink channel for supporting bothgrant-free and grant-based uplink transmissions;

FIG. 13 is a diagram of another embodiment uplink channel for supportingboth grant-free and grant-based uplink transmissions;

FIG. 14. is a diagram of subframe 1401 that includes uplink resourcesthat are available for grant-free and grant-based transmissions

FIG. 15 is a diagram of an embodiment processing system;

FIG. 16 is a diagram of an embodiment transceiver;

FIG. 17 is a diagram of sub-frame structures featuring pilot symbols ator near the beginning of the sub-frame;

FIGS. 18A-18C are diagrams of time-frequency resource allocations in anetwork that supports the coexistence of grant-free and grant-basedtraffic;

FIGS. 18D-18E are diagrams of embodiment resource mapping configurationsfor initial transmissions and retransmissions;

FIG. 19A is a time-frequency resource configuration for a grant-freepartition;

FIG. 19B is a diagram of another embodiment resource mappingconfiguration for initial transmissions and retransmissions;

FIG. 20 is a diagram of another time-frequency resource configurationfor a grant-free partition;

FIGS. 21A and 21B are diagrams of embodiment grant-free time divisionduplex (TDD) frame structures;

FIG. 22 is a diagram of an example of a grant-free TDD frame structure;and

FIG. 23A and 23B are block diagrams of a base station transmitter andreceiver, respectively.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of embodiments of this disclosure are discussed indetail below. It should be appreciated, however, that the conceptsdisclosed herein can be embodied in a wide variety of specific contexts,and that the specific embodiments discussed herein are merelyillustrative and do not serve to limit the scope of the claims. Further,it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of this disclosure as defined by the appended claims. In someembodiments, grant-free uplink transmissions carry ultra-reliable lowlatency communications (URLLC) traffic/data and grant-based uplinktransmissions carry enhanced mobile broadband (eMBB) traffic/data. Othertypes of traffic and data may also be carried by grant-free andgrant-based uplink transmissions.

Grant-based access and grant-free access both have advantages anddisadvantages. For example, grant-free access generally supportslower-latency traffic requirements than grant-based access becausegrant-free access permits data transmissions to be performed withouthaving to request and receive resource grants. However, grant-freeuplink transmissions may collide with one another when two UEs attemptto access the same uplink resource. Those collisions may prevent thebase station from successfully decoding one or both of thetransmissions, which may either result in retransmissions or failure ofthe transmission. For this reason, grant-based uplink transmissions mayprovide higher reliability than grant-free uplink transmissions,particularly when there are large numbers of UEs trying to access thenetwork.

In next generation networks, it may be desirable for grant-based andgrant-free traffic to coexist on the same resources. For example, a BSmay allocate channel resources (e.g., orthogonal frequency divisionmultiplexed (OFDM) symbols, time-frequency resources, etc.) to supportgrant-free uplink transmissions by a group of UEs. The allocation ofchannel resources may be semi-static and/or configured by higher layersignaling or activated by layer 1 signaling. In some instances, the BSmay then schedule one or more of the channel resources in a givensubframe to carry a grant-based uplink transmissions. This may occurwhen, for example, the BS notices that one or more of the channelresources is being accessed infrequently by the group of UEs, oradditional channel capacity for grant-based uplink transmissions isneeded. Scheduling the grant-based uplink transmission over resourcesallocated for grant-free access may effectively increase utilizationefficiency of the channel. However, if a grant-free uplink transmissionis performed over the resource, then the grant-free uplink transmissionmay collide with the grant-based uplink transmission. This may preventthe base station from successfully decoding the grant-free uplinktransmission, and require a retransmission of the grant-free uplinktransmission. It may be possible that grant-free resources are grouped,which may facilitate resource sharing and/or controlling collisionbetween grant-free and grant-based UL transmission. For example, anoriginal grant-free transmission may occur over a first group of timeand/or frequency resources, and grant-free re-transmissions may occurover a second group of time and/or resources. Alternatively, an originalgrant-free transmission and a first set of grant-free re-transmissionsmay occur over a first group of time and/or frequency resources and asecond set of grant-free re-transmissions may occur over a second groupof time and/or frequency resources. In such an example, the first set ofgrant-free re-transmission may refer to first and secondre-transmissions of the original grant-free transmission, and the secondset of grant-free re-transmissions may refer to third and/or laterre-transmissions of the original grant-free transmission. Any othercombinations of grouping re-transmissions into the sets are alsopossible. There can be more than two groups of grant-free time and/orfrequency resources configurations as well. Alternatively, group(s) ofgrant-free resources can be configured based on modulation and codingschemes (MCSs) supported for grant-free transmissions, for example, onegroup is configured for grant-free transmission with a first MCS and asecond group is configured with a second MCS. Alternatively, one groupmay be configured to observe more grant-free transmission than a secondgroup (e.g., more UEs can transmit in one group than other, i.e.,loading can be different). Grant-based UL transmission can be scheduledin at least one group of grant-free time/frequency resources, mentionedabove. These group of grant-free resources can be semi-staticallyconfigured or configured/activated by some layer 1 signaling. Agrant-free UE may or may not be aware of how grouping of the grant-freeresources are obtained. As expected, collision can occur over thegroup(s) that are also configured/used for grant-based UL transmission.

Indeed, the problem may be compounded in instances when the grant-baseduplink transmission spans resource(s) used for the original grant-freeuplink transmission and/or the resource used for the retransmission ofthe grant-free uplink transmission, particularly when the grant-freeuplink transmission carries traffic having low-latency and/orhigh-reliability quality of service (QoS) requirements. Accordingly,techniques are needed for mitigating interference experienced bygrant-free retransmissions when grant-based uplink transmissions arescheduled to resources allocated for grant-free access.

Aspects of this disclosure mitigate interference in a time divisionduplexed frame by altering a transmission parameter of grant-baseduplink transmissions upon determining that a portion of the grant-basedtransmission will coincide with the retransmission of a detectedgrant-free uplink transmission. In this disclosure, the term “grant-freeretransmission” refers to a re-transmission of an initial grant-freetransmission, as may occur when a signal that was communicated as agrant-free uplink transmission over one uplink resource isre-transmitted over another uplink resource.

The grant-free retransmission may be triggered byacknowledgment/negative-acknowledgement (ACK/NACK) signaling from theBS, e.g., receiving a negative acknowledgment (NACK) message, or failingto receive an acknowledgment (ACK) message. Alternatively, apredetermined number of grant-free retransmissions may be triggeredautomatically (e.g., the retransmissions are performed irrespective offeedback from the BS) in order to improve reliability without incurringthe latency associated with waiting for an acknowledgement that theoriginal transmission has been successfully decoded. These automaticre-transmissions may be referred to as “repetitions.” Any discussion ofa grant-free retransmission herein should be understood to refer toeither a first or a subsequent retransmission. The resources over whichthe one or more grant-free retransmissions are performed may bepre-configured (e.g., through a semi-static allocation), in which casethe base station determines the resources based on a priori information.Alternatively, the resources over which the one or more grant-freeretransmissions are performed may be determined according to anidentifier in a pilot symbol of the original grant-free uplinktransmission. This may allow the BS to predict, or otherwise identify,which uplink resources will carry the one or more retransmissions upondetecting the identifier in the pilot symbol. Transmitting theidentifier in the pilot symbol of the original grant-free uplinktransmission may be advantageous because pilot symbols are typicallylower density transmissions than data symbols, which may allow the BS todecode the pilot symbols even when the BS is unable to decode the datasymbols. Additionally, the pilot symbols may be transmitted at or nearthe beginning of the data transmission, in which case transmitting theidentifier in the pilot symbol may allow the BS to obtain the identifierbefore the entire data transmission has been received. The identifier inthe pilot symbol may be a UE identifier, e.g., an RNTI.

The BS may instruct the UE that is performing the grant-based uplinktransmission to alter a transmission parameter of the grant-based uplinktransmission by communicating a downlink control signal over a downlinkresource of the TDD subframe. The term “TDD subframe” refers to asubframe that has at least one uplink resource and at least one downlinkresource. TDD subframes may also include guard intervals and/or guardsymbols between uplink and downlink resources. The term “uplinkresource” refers to any resource over which an uplink transmission isperformed. For example, an uplink resource may be a single OFDM symbol,a group of two or more OFDM symbols, a mini-slot, or a slot or anaggregation of them. Other examples are also possible. Likewise, theterm “downlink resource” may refer to any resource over which a downlinktransmission is performed, e.g., one or more OFDM symbols, a mini-slot,a slot, etc. The downlink control signal may be a UE specific controlsignal or a broadcast or multi-cast control signal, e.g., acell-specific or group-based common control information, etc. In oneembodiment, the downlink control signal instructs the UE to reduce thetransmit power level of the grant-based uplink transmission during theuplink resource carrying the grant-free retransmission. In anotherembodiment, the downlink control signal instructs the UE to mute thegrant-based uplink transmission during the uplink resource carrying thegrant-free retransmission. In such an embodiment, the downlink controlsignal may further instruct the UE to adjust a modulation and codingscheme (MCS) level of the grant-based uplink transmission over otherresources scheduled to carry the grant-based transmission to compensatefor muting the grant-based uplink transmission over the uplink resourcecarrying the grant-free retransmission. In another embodiment, thedownlink control signal instructs the UE to shift the grant-based uplinktransmission to a different uplink resource in the frame. In yet anotherembodiment, the downlink control signal instructs the UE to postpone thegrant-based uplink transmission. In such an embodiment, the downlinkcontrol signal may instruct the UE to postpone the grant-based uplinktransmission until a subsequent subframe (e.g., the next subframe, twosubframes, etc.) or indefinitely until a subsequent grant is received bythe UE. These and other aspects are explained in greater detail below.Although “sub-frames” may have a duration of 1 ms in 4G LTE and NR, itshould be appreciated that the term “sub-frame” is not so limited inthis disclosure, and may have any duration, e.g., 5 ms, 2 ms, 10 ms,etc. In some embodiments, a sub-frame is defined as a specific number ofsymbols or timeslots.

FIG. 1 illustrates a network 100 for communicating data. The network 100comprises a base station no having a coverage area 101, a plurality ofmobile devices 120, and a backhaul network 130. As shown, the basestation no establishes uplink (dashed line) and/or downlink (dottedline) connections with the mobile devices 120, which serve to carry datafrom the mobile devices 120 to the base station no and vice-versa. Datacarried over the uplink/downlink connections may include datacommunicated between the mobile devices 120, as well as datacommunicated to/from a remote-end (not shown) by way of the backhaulnetwork 130. As used herein, the term “base station” refers to anycomponent (or collection of components) configured to provide wirelessaccess to a network, such as an evolved NodeB (eNodeB or eNB) or a gNB,a transmit/receive point (TRP), a macro-cell, a femtocell, a Wi-Fiaccess point (AP), or other wirelessly enabled devices. Base stationsmay provide wireless access in accordance with one or more wirelesscommunication protocols, e.g., long term evolution (LTE), LTE advanced(LTE-A), High Speed Packet Access (HSPA), Wi-Fi 802.11a/b/g/n/ac, etc.As used herein, the term “mobile device” refers to any component (orcollection of components) capable of establishing a wireless connectionwith a base station, such as a user equipment (UE), a mobile station(STA), and other wirelessly enabled devices. In some embodiments, thenetwork 100 may comprise various other wireless devices, such as relays,low power nodes, etc.

Embodiments of this disclosure mitigate interference experienced bygrant-free retransmissions when grant-based uplink transmissions arescheduled in an uplink resource carrying the grant-free retransmission.As used herein, the term “TDD subframe” refers to a subframe that has atleast one uplink resource and at least one downlink resource that istime division duplexed with the uplink resource. TDD subframes may alsoinclude guard intervals/symbols between the uplink and downlinkresources. FIG. 2 is a diagram of an uplink subframe 200 that permitsthe coexistence of grant-based and grant-free uplink transmissions. Asshown, the uplink subframe 200 includes a plurality of downlinkresources 211-213, a plurality of uplink resources 231-236, and aplurality of guard intervals 221, 224, 229. The guard intervals 221,224, 229 separate uplink portions of the subframe 200 from downlinkportions of the subframe 200. In some embodiments, there may also be ashort guard interval that occurs after an uplink resource and prior to adownlink resource.

In this example, the uplink resources 231 and 234 are available forgrant-free uplink transmissions. In some embodiments, the uplinkresources 232, 233, 235, 236 are also available for grant-free uplinktransmission. In other embodiments, the uplink resources 232, 233, 235,236 are not available for grant-free uplink transmission. In thisexample, the uplink resources 234-236 are scheduled to carry agrant-based uplink transmission 252 of a UE to a BS. In this example,the grant-based uplink transmission 252 is shown as being scheduled overa contiguous set of uplink resources 234, 235, 236. It should beappreciated that embodiments of this disclosure are also applicable tosituation in which a grant-based transmission is scheduled overnon-contiguous uplink resources, e.g., the grant-based uplinktransmission 252 may have been scheduled over the uplink resources231-233 in addition to the uplink resources 234-236. The controlsignaling for scheduling the resources 234-236 to carry the grant basedtransmission 252 may be communicated in the downlink resources 211, 212of the subframe 200. Depending on capabilities of the grant-based UEand/or the duration of the guard interval 224, the control signaling forscheduling the resources 234-236 to carry the grant based transmission252 may also be communicated in the downlink resource 213.Alternatively, the control signaling for scheduling the resources234-236 to carry the grant based transmission 252 may be communicated indownlink resources of an earlier frame, or higher-layer signaling.

The base station detects an original grant-free uplink transmission 241in the downlink resource 231. The BS may or may not be able to decodethe original grant-free uplink transmission 241. In one example, theoriginal grant-free uplink transmission 241 collides with a differentgrant-free uplink transmission communicated in the uplink resource 231.In another example, the original grant-free uplink transmission 241collides with in a grant-based uplink transmission scheduled to aportion of the resource 231. The BS then determines that aretransmission 242 of the grant-free uplink transmission 241 will becommunicated over the uplink resource 234 based on an identifier in thegrant-free uplink transmission. The identifier may be carried by a pilotsymbol in the grant-free uplink transmission 241. The BS thencommunicates a downlink control signal 261 over the downlink resource213 that instructs the UE to modify a transmission parameter of thegrant-based uplink transmission 252. Although the grant-based uplinktransmission 252 is shown as beginning after the guard interval 224, itshould be appreciated that in some embodiments, the grant-based uplinktransmission 252 may span downlink resources in multiple sub-frames,e.g., the grant-based uplink transmission 252 could span downlinkresources 232, 233, and 234-236. It should be appreciated thatgrant-free uplink retransmission 242 may be triggered automaticallywithout relying on ACK/NACK signaling in the downlink resource 213. Thedownlink control signal 261 may be a UE-specific control signal or abroadcast control signal. In one embodiment, the downlink control signal261 instructs the UE to reduce the transmission power of the grant-baseduplink transmission 252 during the uplink resource 234. FIG. 3A is agraph of a transmit power level of the grant-based uplink transmission252 during the uplink resources 234, 235, 236 when the transmit powerlevel of the grant-based uplink transmission 252 is lowered during theuplink resource 234 that carries the grant-free uplink retransmission242. Although the grant-free uplink transmission 241 and the grant-freeuplink retransmission 242 are depicted as being transmitted over asingle uplink resource 231 and 234 (respectively), it should beappreciated that grant-free uplink transmission and/or retransmissionsmay span multiple uplink resources.

In another embodiment, the downlink control signal 261 instructs the UEto mute the grant-based uplink transmission 252 during the uplinkresource 234. FIG. 3B is a graph of a transmit power level of thegrant-based uplink transmission 252 during the uplink resources 234,235, 236 when the transmit power level of the grant-based uplinktransmission 252 is muted during the uplink resource 234 that carriesthe grant-free uplink retransmission 242. In yet another embodiment, thedownlink control signal 261 instructs the UE to postpone the grant-baseduplink transmission 252 until a specified or predetermined subsequentframe, or indefinitely until a subsequent grant is received. In oneembodiment, the downlink control signal 261 may also instruct the UE tomute the grant-based uplink transmission 252 during the uplink resource234 and to adjust an MCS parameter (e.g., a coding rate, etc.) of thegrant-based uplink transmission 252 during one or both of the uplinkresources 235, 236 in order to compensate for the muting the grant-baseduplink transmission 252 during the uplink resource 234. In yet anotherembodiment, the downlink control signal instructs the UE to shift theentire grant-based uplink transmission 252 to a different set ofresources in the uplink frame 200.

A base station may perform grant-free activity detection based on acombination of metrics that depend on, for example, loading parametersassociated with grant-free uplink transmissions, a received power levelof one or more grant-free uplink transmissions, and a number of activeUEs, etc. In some embodiments, activity detection is performed toidentify an overlap between grant-based and grant-free traffic. If thenumber of grant-free UEs transmitting exceeds a threshold value, thengrant-based UEs may be instructed to adjust transmission parameters overresources for which grant-free retransmissions are to occur. In someembodiments, the instruction is a multi-level notification that dependson how many metrics for detection are accounted for. When using amulti-level notification, a grant-based UE may be instructed to continueto transmit at the assigned power, to reduce a transmit power level tohalf or any other value, to puncture all or a specified portion of thegrant-free resources, and/or to implement some other interferencemitigation technique.

FIG. 4 is a flowchart of an embodiment method 400 for mitigatinginterference between grant-based uplink transmissions and grant-freeuplink retransmissions, as may be performed by a base station. At step410, the base station detects a grant-free uplink transmission over afirst uplink resource of the subframe. At step 420, the base stationdetermines that a retransmission of the grant-free uplink transmissionwill occur over a second uplink resource in the subframe. In oneembodiment, the first uplink resource over which the grant-free uplinktransmission is detected and the second uplink resource over which theretransmission occurs are orthogonal (i.e., do not overlap) in thetime-domain and/or frequency domain. In another embodiment, the firstuplink resource over which the grant-free uplink transmission isdetected and the second uplink resource over which the retransmissionoccurs are overlap in the time-domain and/or frequency domain.

It should be appreciated that the grant-free uplink transmissiondetected in step 410 may be an original uplink transmission or aretransmission of an original transmission, and the “retransmission”referred to in step 420 may be a first retransmission of the originaluplink transmission or a subsequent retransmission (e.g., second, third,etc.) of the original uplink transmission. At step 430, the base stationtransmits a downlink control signal over a downlink resource of thesubframe that instructs the UE (e.g., a grant-based UE) to adjust atransmission parameter of the grant-based uplink transmission. In anembodiment, the downlink control signal that instructs the UE to adjustthe transmission parameter of the grant-based uplink transmission is aUE-specific or group-specific downlink control information (DCI)message. In another embodiment, the downlink control signal thatinstructs the UE to adjust the transmission parameter of the grant-baseduplink transmission is transmitted in a UE-specific region or agroup-specific region of a downlink frame.

In some embodiments, a base station will re-configure a set of resourcesassigned to carry grant-free uplink transmissions to mitigateinterference between grant-based and grant-free uplink transmissions.FIG. 5 is a diagram of subframe 501 during which a set of resources forcarrying grant-free uplink transmissions is reconfigured by a downlinkcontrol signal 561. The control signal 561 can be UE-specific orgroup-common. As shown, the TDD subframe 501 includes a plurality ofdownlink resources 511-512, a plurality of uplink resources 531-536, anda guard interval 521. The guard interval 521 separates uplink portionsof the subframe 501 from downlink portions of the subframe 501. In thisexample, a downlink control signal 561 is transmitted over the downlinkresource 512 to reconfigure an access space available for grant-freeuplink transmission. The access space includes an initial set ofresources 550 prior to reconfiguration, and an updated set of resources551 following the reconfiguration. In this example, the initial set ofresources 550 does not overlap with the updated set of resources 551. Inother examples, the initial and updated sets of resources partiallyoverlap such that the sets both include least one common uplinkresource. In some embodiments, the reconfiguration may be prompted byscheduling of a grant-based uplink transmission over one or both of theuplink resources 531, 532. Re-configuration may be performed for wholeor part of the configured grant-free access space, e.g., set oftime-frequency resources available for grant-free transmissions, etc.Although FIG. 5 illustrates a re-configuration of resources availablefor grant-free transmission in the time domain such that the updated setof resources 551 spans a different set of time-domain resources than theinitial set of resources 550, it should be appreciated that someembodiments may reconfigure resources available for grant-freetransmission in the frequency domain such that the resulting updated setof resources spans a different set of frequency-domain resources (e.g.,sub-carrier frequencies) than the initial set of resources. It shouldalso be appreciated that some embodiments may reconfigure resourcesavailable for grant-free uplink transmission in both the time-domain andthe frequency-domain such that the resulting updated set of resourcesspans a different combination of time-frequency resources than theinitial set of resources. Other examples are also possible. For example,embodiments may reconfigure resources available for grant-free uplinktransmission in the code domain and/or spatial domain.

FIG. 6 is a flowchart of an embodiment method 600 for mitigatinginterference between grant-based and grant-free uplink transmissions, asmay be performed by a base station. At step 610, the base stationschedules a first uplink resource to carry a grant-based uplinktransmission of a first user equipment (UE). The first uplink resourceis included in an initial set of uplink resources available forgrant-free uplink transmissions. At step 620, the base station sends asignal that updates the set of uplink resources for grant-free uplinktransmissions. In one example, the signal is a downlink controlinformation (DCI) message. In another example, the signal is a radioresource control (RRC) message. The updated set of uplink resourcesexcludes the first uplink resource.

In some examples, a grant-based transmission may be scheduled overmultiple uplink resources. FIG. 7 is a diagram of a set of resourcesscheduled to carry a grant-based uplink transmission of a UE. In anembodiment, a grant-based UE monitors DL control for possible grant-freetransmission. If a grant-free transmission is detected, the BS mayadjust (e.g., postpone) a grand-based transmission of the grant-based UEin one or more UL resources. Those UL resources are used by grant-freetransmission. The grant-based transmission may resume after grant-freetransmissions are no longer using the resources scheduled for thegrant-based transmission.

Although many of the embodiments for coexistence of grant-free andgrant-based transmissions are shown in TDD channels, it should beappreciated that those embodiments can also be used for coexistence ofgrant-free and grant-based transmissions in frequency division duplexed(FDD) channels. Additional techniques for the coexistence of grant-freeand grant-based transmissions in TDD channels are described in U.S.Non-Provisional Application No. 15/223,690, filed on Jun. 29, 2016entitled “System and Method for Retransmission of Grant-Free Traffic,”which is hereby incorporated by reference in its entirety.

Embodiments of this disclosure provide techniques for dynamicallysignaling when a retransmission of a grant-free uplink transmission isto occur over a subset of uplink resources scheduled to carry agrant-based uplink transmission of a UE. This may allow the UE tomitigate, or avoid, interference between the grant-based uplinktransmission and the grant-free uplink transmission by puncturing aportion of the grant-based uplink transmission that corresponds to thesubset of uplink resources that will carry the grant-free uplinktransmission.

In one embodiment, the indication is transmitted over a control channelthat is associated with a different UE than the UE which is scheduled toperform the grant-based uplink transmission. In such an embodiment, theUE scheduled to perform the grant-based uplink transmission may beconfigured to monitor the control channel of the other UE. The controlchannel over which the indication is transmitted may be a UE-specificcontrol channel associated with a different UE than the UE which isscheduled to perform the grant-based uplink transmission, or agroup-specific control channel associated with a group of UEs thatexcludes the UE that is scheduled to perform the grant-based uplinktransmission. The indication could also be communicated over a controlchannel associated with the UE scheduled to perform the grant-basedtransmission.

In one embodiment, the control channel that carries the indication isseparately configured from other control channels that provide DL or ULscheduling grants and/or HARQ feedback of UL transmissions. At least onegrant-based UE can be configured to monitor one or multiple controlchannels which provide indication(s) for UL resource adjustment ofgrant-based UEs. In another embodiment, a control channel configured forsending DL or UL grant or HARQ feedback information of UL transmissioncan be reused for sending the indication. In the case of reusing acontrol channel for DL or UL grant or HARQ feedback, the control channelmay be monitored not only by the grant-based UEs whose UL transmissioncould be adjusted, but also by other grant-free and/or grant-based UEsthat receive grant or HARQ feedback information. For example, A/Nfeedback of grant-free transmissions can be monitored by grant-based UEsif they are scheduled in a time-frequency resource where UL grant-freetransmissions can be expected.

FIG. 8 is a diagram of a frame format 800 for dynamically notifying a UEthat a retransmission of a grant-free uplink transmission will occurover resources scheduled to carry a grant-based uplink transmission ofthe UE. As shown, in the frame format 800, downlink transmissions arecommunicated over downlink subframes 801, 802, and uplink transmissionsare communicated over uplink subframes 803, 804. The downlink subframes801, 802 include control regions 811, 821, respectively. The controlregion 811 carries signaling that assigns a set of resources in theuplink subframe 804 to carry a grant-based uplink transmission 826. Itshould be appreciated that location of grant-based control informationat the beginning of a sub-frame is an example only, and other locationsare also possible. In some embodiments, a grant-based UE can beconfigured to monitor UL grant in any symbol(s) of a DL sub-frame. Inthis example, a base station detects the grant-free uplink transmission818, determines that a retransmission 828 of the grant-free uplinktransmission 818 is to occur over a subset of the resources scheduled tocarry the grant-based uplink transmission 826, and sends an indicationover a configured control channel 823 in the downlink subframe 802. Thecontrol channel 823 may be a UE-specific or group-specific controlchannel. The time frequency resources where 823 is located may or maynot be shared with other control channel and/or downlink datatransmissions. The indication sent over the control channel 823 prompts,or otherwise instructs, a UE scheduled to perform the grant-based uplinktransmission 826 to puncture a portion 827 of the grant-based uplinktransmission 826 corresponding to the subset of resources that willcarry the retransmission 828 of the grant-free uplink transmission 818.Although the retransmission 828 is shown as a grant-free uplinktransmission in the example depicted by FIG. 8, it should be appreciatedthat, in other examples, a “retransmission of a grant-free uplinktransmission” may itself be a grant-based uplink transmission. Thegrant-based uplink transmission 826 may originate from a different UEthan the grant-free uplink transmission 818 and/or the retransmission828 of the grant-free uplink transmission. Alternatively, thegrant-based uplink transmission 826 may originate from the same UE asthe grant-free uplink transmission 818 and/or the retransmission 828. Itshould be appreciated that the control channel 823 may be any controlchannel, including a control channel that is assigned to the UE which isscheduled to perform the grant-based uplink transmission 826 and/or acontrol channel that is different than, or otherwise not located within,a downlink control channel associated with the UE scheduled to performthe grant-based uplink transmission 826. In one example, the controlchannel 823 is a control channel associated with the UE that transmittedthe grant-free uplink transmission 818. In such an example, the controlchannel 823 may be an acknowledgment negative-acknowledgment (ACK/NACK)channel associated with the UE that transmitted the grant-free uplinktransmission 818, and grant-based UEs may monitor that ACK/NACK channelfor negative acknowledgement (NACK) messages that indicate that agrant-free uplink transmission 818 was not successfully received by thebase station, in which case the grant-based UEs may determine that aretransmission 828 will occur in the uplink subframe 804. In anotherexample, the control channel 823 is associated with a differentgrant-based UE. The control channel 823 may have a similar structure tothe control channel that provides downlink or uplink scheduling grants(e.g., a PDCCH) if the control channel is UE specific. Alternatively, ifthe control channel 823 is monitored by a group of grant-based UEs, thenthe control channel 823 may have a structure of a group-common controlchannel (e.g., group-PDCCH), e.g., checked by a group RNTI.

In another embodiment, the indication is transmitted over a downlinkdata channel of a frame or subframe. FIG. 9 is a diagram of anotherframe format 900 for dynamically notifying a UE that a retransmission ofa grant-free uplink transmission will occur over resources scheduled tocarry a grant-based uplink transmission of the UE. Like the frame format800, in the frame format 900, a downlink subframe 901 includes a controlregion 911 that carries control signaling assigning a set of uplinkresources in an uplink subframe 904 to carry a grant-based uplinktransmission 926, and the uplink subframe 903 carries a grant-freeuplink transmission 918. The base station may determine that aretransmission 928 of the grant-free uplink transmission 918 is to occurover a subset of the resources scheduled to carry the grant-based uplinktransmission 926 in the uplink subframe 904.

However, unlike the frame format 800, the base station sends anindication of the retransmission 918 in a control channel 923 within thedata channel in the downlink subframe 902. The resources may be sharedbetween the control channel 923 and one or multiple downlink datatransmission. In one embodiment, the control channel 923 may residewithin pre-configured time-frequency resources that are known to thegrant-based UE(s) monitoring the indication signaling. In oneembodiment, the control channel 923 may puncture one or multiple ongoingdownlink transmissions. In another embodiment, the control channel 923can be super-imposed with other downlink transmissions. In yet anotherembodiment, the control channel 923 may align with a punctured portionof a downlink transmission (not shown) in the downlink subframe 902.

Control channels 823 and 923 can have the same structure or differentstructures. For example, control channel 823 can have a conventionalPDCCH structure where CRC is appended to distinguish the PDCCH in asearch space where other PDCCH can also be sent which may or may nothave the same payload size. Control channel 923 may have a preconfiguredlocation that is monitored by grant-based UEs for indication signaling.When no indication is sent, the resource set of control channel 923 canbe used for other DL transmissions. Because this resource set ispre-configured, CRC may not need to be appended because the UEs may notneed to distinguish different control signaling in the pre-configuredresource. Alternatively, the control channel 923 can be encodedsimilarly to data transmissions. In one example, the control channel 923is not appended with UE or group identifier information. The indicationprompts, or otherwise instructs, a UE scheduled to perform thegrant-based uplink transmission 926 to puncture a portion 927 of thegrant-based uplink transmission 926 corresponding to a subset ofresources that will carry the retransmission 928 of the grant-freeuplink transmission 918. In one embodiment, control channel 923 locatedin a downlink data channel may be associated either with the UE that isscheduled to transmit the grant-based uplink transmission 928 or with adifferent UE, such as a UE that transmitted the grant-free uplinktransmission 918 or a different grant-based UE. The control channel 923may carry a broadcast, multi-cast, or unicast signal.

The control channels 823 or 923 in FIGS. 8 and 9 may have a duration ofa mini-slot. A mini slot consists of fewer symbols than a slot. Uplinkand downlink subframes shown in FIGS. 8 and 9 may comprise a slot or anaggregation of slots or aggregation of slot(s) and mini-slot(s).

In one embodiment, the content or the granularity of indication oftime-frequency resources in the provided signaling can be configurable.The signaling may indicate one or more time-domain resourcesfrequency-domain resources, time-frequency resources, or code-domainresources. In the time domain, the granularity can be one or acombination/group of symbols, slots, mini-slots, or units of time (e.g.,one or more us, etc.). In the frequency domain, the granularity can beone or a combination/group of PRBs, sub-bands, or units of frequency (inHz). In the code domain, the signaling may indicate one or acombination/group of code-blocks.

In one embodiment, grant-free UEs may receive layer one signaling whichmay update transmission parameters. The layer one signaling can bereceived before or after an initial grant-free transmission. In oneexample, after the base station identifies that a grant-freetransmission of a UE may collide (e.g., persistently or otherwise) witha grant-based transmission, the UE performing the grant-freetransmission may receive dynamic signaling which may update transmissionparameters, for example, MCS, hopping pattern, time-frequency resources,number of repetitions, power etc. The signaling can be UE specific orgroup-based.

In one embodiment, both grant-free and grant-based transmissions mayoriginate from the same UE. In such an embodiment, the UE may not needto monitor a control channel for an indication of adjustment of ULresources or transmission parameters. This is because both grant-basedand grant-free transmissions are being transmitted from the same UE, andas a result, the UE knows the time-frequency resources used forgrant-free transmissions and time-frequency resources scheduled forgrant-based transmissions. The grant-free transmission can be initiatedbased on semi-static configuration only or may use a separate activationcontrol signal after semi-static configuration. Depending upon how thegrant-free transmission is configured, the UE behavior can beidentified. In one embodiment, if an activation signal is configured butnot received and if a grant-free packet arrives at the UE, then the UEmay continue grant-based transmission and wait for the next activationsignal to transmit the grant-free packet. In another embodiment, if agrant-free packet arrives at the UE and if an activation signal isreceived or a grant-free transmission can be initiated followingsemi-static configuration only, several options for UE behavior can beidentified for the UE that also transmits grant-based traffic, suchas 1) If there is a grant-based transmission on-going, the grant-basedand grant-free transmissions can be super-imposed over the configuredtime-frequency resources for grant-free transmission. The transmit powerof the grant-based transmission may be adjusted over the area ofsuper-position. Alternatively, 2) the UE may puncture or postpone thegrant-based transmission over the area of overlap. The same referencesignal/sequence can be used for both transmissions, or the grant-freetraffic may have its own reference sequence embedded in itstransmission. If the grant-free transmission has a higher reliabilityrequirement, the grant-free transmission can be decoded using referencesignals in both grant-based and grant-free transmissions, which mayimprove channel reliability/robustness. As mentioned above, thereference sequence may also provide a UE identification. If the samereference sequence (RS) is used for both grant-based and grant-freetraffic (e.g., front loaded RS in a grant-based transmission), the UEmay provide additional information to indicate the existence ofgrant-free traffic. An indication may be provided in an uplink controlchannel so that BS identifies the existence of grant-free traffic from aUE that is transmitting grant-based traffic concurrently. If thetime-frequency resources of grant-free traffic are configured, a one-bitindication can notify the BS of the existence of grant-free traffic. TheBS can attempt to decode the grant-free traffic in the configuredtime-frequency resources. If the time-frequency resources of thegrant-free traffic are not configured, a multi-bit indication can beprovided to identify the time-frequency resources in which a grant-freetransmission has occurred. The indication can be sent during thegrant-free transmission or after, depending upon the latency requirementof the grant-free transmission.

In one embodiment, one UE may transmit a first and a second type ofgrant-free traffic, having different latency requirements. In oneexample, the first type of grant-free traffic is eMBB and the secondtype is URLLC. The UE may be configured with the same or different RSfor transmission of different types of grant-free traffic. In oneexample, the UE ID can be mapped to multiple RSs. One set of RSs can beused for the first type of grant-free traffic and a second set of RSscan be used for the second type of grant-free traffic. Because differenttypes of grant-free traffic can have different semi-staticconfigurations, such as the number of grant-free repetitions, it can beuseful for the BS to identify which type of grant-free traffic isreceived from the UE, if the UE can send multiple types of grant-freetraffic. Here, the RS can be used not only as a UE identifier but alsoas an identification of the service type. Alternatively, the servicetype or grant-free traffic type can be indicated in a separate channel,for example, in a UL control channel. In one example, grant-freetransmissions of the first type can have a longer duration thangrant-free transmissions of the second type. The mechanisms mentioned inthe above paragraph for concurrent transmission of multiple traffictypes can be applicable here as well. The UE canpuncture/postpone/super-impose multiple grant-free transmissions. RSscan be shared between multiple grant-free transmissions or eachgrant-free transmission can be embedded with its own RS. The indicationtransmission from the UE to notify the BS of the existence of agrant-free transmission mentioned above can be applicable here as well.

In one embodiment, different UEs may transmit different traffic types,for example, eMBB/URLLC/mMTC, over shared time-frequency resourceswithout receiving a resource grant. For example, relatively low-payloadeMBB packets can be transmitted in a grant-free manner to reducesignaling overhead. Different traffic types may have differenttransmission parameters (e.g., RRC configurations, time-frequencyresources, RS, MCS, number of repetitions, hopping pattern, powercontrol parameters, maximum number of HARQ processes, etc.), differentquality of service requirements (e.g., latency, throughput ,reliability, coverage), and/or different grant-free transmissionprocedures (e.g., grant-free transmissions of one type of traffic may beinitiated by RRC signaling, whereas grant-free transmissions of anothertype of traffic may be initiated by layer one signaling). In oneexample, a first UE and a second UE transmits packet without grant in ashared time-frequency resource. The base station has detected theactivity of the first UE. After detecting the activity of the second UEin resources overlapping with the transmission of the first UE, the basestation may provide signaling to either or both of the first or thesecond UE, to adjust or stop or postpone transmission by either UE inone or more subsequent intervals. In one example, the base station mayprovide a de-activation signal to the first or the second UE to stoptransmission in shared resources or areas of potential overlap. Inanother example, a signaling may be provided to the first UE when theactivation signal is sent to the second UE before the second UE startsgrant-free transmission so that the first UE may adjust/stop/postponeits transmission. The signaling may optionally include an indicationrelated to time-frequency resources where two transmissions areoverlapping. The indication signaling mechanisms discussed above in thecontext of grant-based and grant-free transmission coexistence can beapplied here, such that indication signaling can be monitored by a UEconfigured for grant-free transmission as well.

In some examples, grant-free transmissions of different traffic typesand/or grant-free transmissions from different groups of UEs maypotentially occur over shared resources. In such examples, the grantfree transmissions may be configured and/or activated via differenttypes of signaling. In one example, a first group of UEs is configuredwith RRC configuration and L1 activation, and a second group of UEs isconfigured with RRC configuration and L1 activation. In another example,a second group of UEs is configured with RRC configuration and does notrequire any L1 activation signaling before starting transmission, and asecond group of UEs is configured with RRC configuration and L1activation. In yet another example, a first group of UEs is configuredwith RRC configuration and L1 activation, and a second group of UEs isconfigured with RRC configuration and does not require any L1 activationsignaling before starting transmission. In yet another example, a firstgroup of UEs is configured with RRC configuration and does not requireL1 activation before starting transmission, and a second group of UEs isconfigured with RRC configuration and does not require any L1 activationbefore starting transmission. For each of these examples, either groupor both groups of UEs may monitor signaling to adjust ongoing and/orsubsequent grant-free transmissions, which may be sent if the basestation detects a suspected or persistent collision. The adjustmentsignaling may instruct the UE to puncture, postpone, and/or suspend allor a part of a transmission and/or to change transmission parameters(e.g., MCS, hopping patterns, number of repetitions, power control,etc.). The signaling can be UE-specific or group-specific signaling. Thesignaling can be independent of activation/de-activation signaling (ifconfigured) or signaling can be conveyed by activation/de-activationsignaling. In one example, activation/de-activation signaling can beaugmented to include an instruction to adjust one or more transmissionparameters. Similar mechanisms can be extended when there are more thantwo groups of UEs transmitting grant-free traffic and each group istransmitting a different traffic type which may have different RRCconfigurations.

In one embodiment, the indication and/or activation/deactivationsignaling can be monitored by grant-based or grant-free UEs either in anactive state or an inactive state.

It should be appreciated that the indication signaling mechanisms can beapplicable to any of the embodiments described in this application,including those in which the signaling is monitored either by agrant-free or grant-based UE. The type (e.g., UE specific/group-based),content (e.g., payload and/or granularity of time-frequency resourceindication and/or indication of adjustment in transmission parameters)and/or structure (e.g., follow PDCCH structure or not) of indicationsignaling are discussed in a general context which is not limited to anyparticular coexistence scenario.

FIG. 10 is a flowchart of an embodiment method 1000 for puncturing agrant-based uplink transmission to mitigate interference between thegrant-based uplink transmission and a grant-free uplink transmission, asmay be performed by a UE. At step 1010, the UE receives a schedulinginstruction indicating that uplink resources are scheduled to carry agrant-based uplink transmission of the UE. At step 1020, the UE monitorsone or more downlink resources in a downlink control channel for anindication that a retransmission of a grant-free uplink transmission isto occur over a subset of the uplink resources scheduled to carry thegrant-based uplink transmission of the UE. At step 1030, the UEpunctures a portion of the grant-based uplink transmission correspondingto the subset of uplink resources in response to detecting theindication that the grant-free uplink transmission is to occur over thesubset of uplink resources.

FIG. 11 is a flowchart of an embodiment method 1100 for dynamicallynotifying a UE that a retransmission of a grant-free uplink transmissionwill occur over resources scheduled to carry a grant-based uplinktransmission of the UE, as may be performed by a base station. At step1110, the base station determines that a retransmission of a grant-freeuplink transmission will occur over a subset of uplink resourcesscheduled to carry a grant-based uplink transmission of a UE. At step1120, the base station transmits an instruction to the UE to puncture aportion of the grant-based uplink transmission that corresponds to thesubset of uplink resources over which the retransmission of thegrant-free transmission will occur.

In some embodiments, grant-based uplink transmissions are strategicallyscheduled over uplink resources that are less likely than other uplinkresources to carry grant-free uplink transmissions. FIG. 12 is a diagramof an embodiment uplink channel 1200 for supporting both grant-free andgrant-based uplink transmissions. In this example, different groups ofgrant-free UEs (UE1-UE 14) are assigned to different access spaces1211-1241 in an uplink channel 1200. For instance, a group of two UEs(UE13, UE14) is assigned to the access space 1211, and as a result, UE13and UE14 are permitted to transmit grant-free uplink transmissions overuplink resources in the access space 1211. Likewise, a group of four UEs(UE4, UE8, UE9, and UE12) are assigned to the access space 1212, whichallows UE4, UE8, UE9, and UE12 to transmit grant-free uplinktransmissions over uplink resources in the access space 1212. Similarly,a group of four UEs (UE3, UE6, UE12, and UE13) are assigned to theaccess space 1213, a group of four UEs (UE9, UE10, UE11, and UE12) areassigned to the access space 1221, a group of four UEs (UE3, UE7, UE11,and UE13) are assigned to the access space 1222, a group of two UEs (UE2and UE7) are assigned to the access space 1223, a group of four UEs(UE5, UE6, UE7, and UE8) are assigned to the access space 1231, a groupof four UEs (UE2, UE6, UE10, and UE14) are assigned to the access space1232, a group of four UEs (UE4, UE5, UE11, and UE14) are assigned to theaccess space 1233, a group of four UEs (UE1, UE2, UE3, and UE4) areassigned to the access space 1241, a group of two UEs (UE1 and UE5) areassigned to the access space 1242, and a group of four UEs (UE1, UE8,UE9, and UE10) are assigned to the access space 1243.

To reduce the likelihood of collisions between grant-free uplinktransmissions and grant-based uplink transmissions, grant basedtransmissions may be scheduled in access spaces that are assigned tosmaller groups of grant-free UEs. Grant-free resources may be configuredin different parts and each part may observe a loading of traffic thatis different than other pails. In this example, the access spaces 1211,1223, and 1242 are assigned smaller groups of grant-free UEs than theaccess spaces 1212-1222, 1231-1241, and 1243, and as a result, agrant-based uplink transmission by UE91 is scheduled in access space1211, a grant-based uplink transmission by UE92 is scheduled in accessspace 1242, and a grant-based uplink transmission by UE93 is scheduledin access space 1223. Although access spaces having smaller groups ofgrant-free UEs may generally be given priority in terms of grant-basedscheduling, it should be appreciated that access spaces assigned tolarger groups of grant-free UEs may also be used to carry grant-baseduplink transmissions when the demand for grant-based resources exceedsthe capacity of the access spaces having smaller groups of grant-freeUEs.

In some embodiments, an uplink channel is divided into regions assignedfor initial grant-free uplink transmissions and regions assigned forretransmissions of grant-free uplink transmissions. In such anembodiment, regions assigned to, or otherwise used for, theretransmissions may be given priority in terms of grant-based schedulingover the regions used for initial grant-free uplink transmissions,because base stations may be able to predict the retransmissions anddelay, or otherwise adjust, the grant-based uplink transmissions tomitigate interference between the retransmissions and the grant-baseduplink transmissions. FIG. 13 is a diagram of an embodiment channelconfiguration 1300 for supporting both grant-free and grant-based uplinktransmissions.

In this example, regions 1331-1344 are available for initial grant-freeuplink transmissions, regions 1321-1324 are available for firstretransmissions of initial grant-free transmissions, and regions1311-1314 are available for second retransmissions of initial grant-freetransmissions.

In one embodiment, grant-based transmissions are scheduled primarilyover the regions 1311-1314 associated with the second re-transmission ofgrant-free transmissions, and/or regions of subsequent transmissions(e.g., third re-transmissions, fourth re-transmissions, etc.). Thisallows the base station to predict when a retransmission of a grant-freeuplink transmission will interfere with a previously scheduledgrant-based uplink transmission of a UE, and instruct the UE tocompensate (e.g., delay, puncture, etc.) the grant-based uplinktransmission accordingly to mitigate, or prevent, interference betweenthe grant-based uplink transmission and the retransmission of thegrant-free uplink transmission.

In another embodiment, regions 1334-1341 may be used exclusively forgrant-free transmissions and/or re-transmissions of grant-freetransmissions, and regions 1311-1314 may be used for both grant-basedtransmissions and re-transmissions of grant-free transmissions. In onespecific example, 1324-1341 can be used for initial/original grant-freetransmission and some subsequent retransmissions/repetitions, e.g.,first or first and second re-transmissions, and 1311-1314 can be usedfor some later re-transmissions that can occur after those configured toappear in 1324-1341 region, e.g., third or later re-transmissions (whichcan be grant-free or grant-based) can occur over 1311-1314.

In yet another embodiment, one region is used exclusively for grant-freetransmissions and/or re-transmissions of grant-free transmissions,another region is used for both grant-based transmissions andre-transmissions of grant-free transmissions, and yet another region isused exclusively for grant-based transmissions.

In this example, a base station detects an initial grant-free uplinktransmission 1301 in the region 1341 and/or a first retransmission 1302,of the initial grant-free uplink transmission 1301, in the region 1322,and determines that a second retransmission 1303, of the initialgrant-free uplink transmission 1301, will occur in the region 1313.These determinations may be based on a pre-configured mapping and/orsemi-static resource configuration. A grant-based uplink transmission1306 of a UE was previously scheduled to occur in the region 1313. Thebase station communicates an indication that instructs, or otherwiseprompts, the UE to postpone the grant-based uplink transmission 1306until the region 1314, thereby avoiding a collision between thegrant-based uplink transmission 1306 and the second retransmission 1303of the initial grant-free uplink transmission 1301. Although the firstretransmission 1302 and the second retransmission 1303 are depicted asgrant-free transmissions in this example, it should be appreciated that,in other examples, the first retransmission 1302 and/or the secondretransmission 1303 may be grant-based uplink transmissions.

The downlink control signal that notifies a grant-based UE that aretransmission of a grant-free transmission will occur over a resourcepreviously scheduled to the grant based UE may be UE specific orgroup-specific signaling. The signaling can be sent as often as everygrant-free transmission interval. Different diversity configurations(e.g., transmit diversity, frequency diversity, etc.) and/or encodingand precoding configurations (e.g., low MCS with or withoutinterleaving, beamforming, etc.) may be used to increase the reliabilityof the downlink control signal. The location of the uplink preemptionindication can be in a PDCCH region located in the first few symbols ofa slot or, alternatively, in a PDCCH region that occurs in subsequentsymbols of a slot. Alternatively, the indication may be encoded andtransmitted over PDSCH resources with the same or a different MCScompared to other PDSCH transmissions. The grant-based UE which isscheduled in a shared region can be configured to monitor downlinkcontrol signaling for adjusting an ongoing transmission. The location(s)in which a UE is to monitory for uplink preemption indications may beconfigured via UE specific or group-specific control signaling. In oneexample, a monitoring interval is configured in terms of number ofsymbols or slots, or a combination thereof.

The control channel used for indication may or may not overlap withother control channels present in the symbol(s) where the indication issent. In one example, a group-common control signal can be transmittedas often as every grant-free interval, e.g., some control resource setsmay have to be monitored by grant-based UEs at mini-slot granularity.Group-specific control signaling that carries UL pre-emption indicationscan be transmitted inside or outside the PDCCH region of a slot. In oneexample, the group-common signaling can be provided in the same controlregion where the grant for URLLC UL transmission is provided. A DL URLLCinterval may be different than an UL URLLC interval. Resource locationsthat are monitored for UL pre-emption indications may correspond to atime scale of the UL URLLC interval. To match that timeline, it mightnot always be possible to send an uplink preemption indication signal inthe PDCCH region of DL URLLC interval, for example if the downlink anduplink intervals are different. Every x μs where x=UL URLLC interval,the indication may be monitored. An uplink preemption indication signalcan be detected in a coherent manner or a non-coherent manner. Thepre-emption indication signal can be sent in a reserved resource whichis not used for DL data transmission. Alternatively, the configuredresource for sending the indication control can be used for datatransmission when the indication is not sent. In another example, DLdata transmission and indication control may be super-imposed in atime-frequency resource. There can be one group-common control signalsent every x μs interval. A group-specific control signal may bere-transmitted over multiple locations in the frequency domain of ashared channel. A group-specific control signal may indicate a bitmap oftime-frequency information of the slot where pre-emption will occur. Thetime granularity of the bitmap can be a symbol group, and the frequencygranularity of the bitmap can be a PRB group or a sub-band BW.Alternatively, multiple group-common indications can be sent based on BWpartitions of the carrier or system BW. Each group-common indication canprovide pre-emption information over a BW partition for the slot whereUL pre-emption will occur.

The configuration of the indication and search space can be notifiedeither via system information or RRC signaling. The configurationincludes how many bits, and which BW partition it is intended for. Thesearch space provides the time-frequency location of the indication.

eMBB UEs are configured to monitor pre-emption indications, andsignaling that configures the UEs can be higher layer signaling ordynamic signaling. Higher layer signaling includes system informationblock and RRC signaling. This configuration signaling can be implicit orexplicit. For example, it can be explicitly or implicitly derived fromsystem information or DCI of UL grant or RRC signaling.

In addition to time-frequency information, power control command mayalso be sent as part of the indication. For example, the signaling caninclude an instruction to the UE to selectively reduce power over theindicated region. For four quantized power levels, a four bit indicationcan be included.

In another example, HARQ feedback (as part of UL control information) ofDL URLLC traffic can also trigger pre-emption of resources from latencytolerant UL traffic, either in the data region (i.e., PUSCH) or in adesignated control region (i.e., PUCCH). A base station can signal tolatency tolerant UEs in DL whether any adjustment is necessary (e.g.,postpone data or defer some uplink control information (UCI) dependingon where pre-emption is signaled) in their UL transmission. Theindication signal may be triggered by detecting UL URLLC traffic, or byfeedback of DL URLLC, and a unified indication channel can be used forthis purpose. The indication channel is unified in the sense that eitherUL control or data transmission of URLLC traffic may causepre-emption/adjustment/modification of UL control or data transmissionof eMBB traffic.

FIG. 14. is a diagram of subframe 1401 that includes uplink resourcesthat are available for grant-free and grant-based transmissions. Asshown, the subframe 1401 includes downlink resources 1410, uplinkresources 1430, and a guard interval 1420 positioned in-between thedownlink resources 1410 and the uplink resources 1430. The uplinkresources 1430 include a region 1431 reserved exclusively for grant-freetransmissions, a region 1432 available for both grant-free andgrant-based transmissions, a region 1433 that is available exclusivelyfor grant-based transmissions, and a region 1434 that carries UCI and/orphysical uplink control channel (PUCCH) signaling. In this example, theregions 1431, 1432, 1433, 1434 are frequency division multiplexed withone another. Other examples are also possible. For example, some uplinkregions of a subframe may be frequency division multiplexed with oneanother, and other uplink regions of the same subframe may be timedivision multiplexed with one another. In a specific example, for agiven interval X ms or K symbols, one portion of the interval mayinclude four partitions as listed above, and another portion of theinterval may include only a single partition, e.g., the last symbol ofan interval can be used for control only.

FIG. 15 is a block diagram of an embodiment processing system 1500 forperforming methods described herein, which may be installed in a hostdevice. As shown, the processing system 1500 includes a processor 1504,a memory 1506, and interfaces 1510-1514, which may (or may not) bearranged as shown in FIG. 15. The processor 1504 may be any component orcollection of components adapted to perform computations and/or otherprocessing related tasks, and the memory 1506 may be any component orcollection of components adapted to store programming and/orinstructions for execution by the processor 1504. In an embodiment, thememory 1506 includes a non-transitory computer readable medium. Theinterfaces 1510, 1512, 1514 may be any component or collection ofcomponents that allow the processing system 1500 to communicate withother devices/components and/or a user. For example, one or more of theinterfaces 1510, 1512, 1514 may be adapted to communicate data, control,or management messages from the processor 1504 to applications installedon the host device and/or a remote device. As another example, one ormore of the interfaces 1510, 1512, 1514 may be adapted to allow a useror user device (e.g., personal computer (PC), etc.) tointeract/communicate with the processing system 1500. The processingsystem 1500 may include additional components not depicted in FIG. 15,such as long term storage (e.g., non-volatile memory, etc.).

In some embodiments, the processing system 1500 is included in a networkdevice that is accessing, or part otherwise of, a telecommunicationsnetwork. In one example, the processing system 1500 is in a network-sidedevice in a wireless or wireline telecommunications network, such as abase station, a relay station, a scheduler, a controller, a gateway, arouter, an applications server, or any other device in thetelecommunications network. In other embodiments, the processing system1500 is in a user-side device accessing a wireless or wirelinetelecommunications network, such as a mobile station, a user equipment(UE), a personal computer (PC), a tablet, a wearable communicationsdevice (e.g., a smartwatch, etc.), or any other device adapted to accessa telecommunications network.

In some embodiments, one or more of the interfaces 1510,1512, 1514connects the processing system 1500 to a transceiver adapted to transmitand receive signaling over the telecommunications network. FIG. 16 is ablock diagram of a transceiver 1600 adapted to transmit and receivesignaling over a telecommunications network. The transceiver 1600 may beinstalled in a host device. As shown, the transceiver 1600 comprises anetwork-side interface 1602, a coupler 1604, a transmitter 1606, areceiver 1608, a signal processor 1610, and a device-side interface1612. The network-side interface 1602 may include any component orcollection of components adapted to transmit or receive signaling over awireless or wireline telecommunications network. The coupler 1604 mayinclude any component or collection of components adapted to facilitatebi-directional communication over the network-side interface 1602. Thetransmitter 1606 may include any component or collection of components(e.g., up-converter, power amplifier, etc.) adapted to convert abaseband signal into a modulated carrier signal suitable fortransmission over the network-side interface 1602. The receiver 1608 mayinclude any component or collection of components (e.g., down-converter,low noise amplifier, etc.) adapted to convert a carrier signal receivedover the network-side interface 1602 into a baseband signal. The signalprocessor 1610 may include any component or collection of componentsadapted to convert a baseband signal into a data signal suitable forcommunication over the device-side interface(s) 1612, or vice-versa. Thedevice-side interface(s) 1612 may include any component or collection ofcomponents adapted to communicate data-signals between the signalprocessor 1610 and components within the host device (e.g., theprocessing system 1500, local area network (LAN) ports, etc.).

The transceiver 1600 may transmit and receive signaling over any type ofcommunications medium. In some embodiments, the transceiver 1600transmits and receives signaling over a wireless medium. For example,the transceiver 1600 may be a wireless transceiver adapted tocommunicate in accordance with a wireless telecommunications protocol,such as a cellular protocol (e.g., long-term evolution (LTE), etc.), awireless local area network (WLAN) protocol (e.g., Wi-Fi, etc.), or anyother type of wireless protocol (e.g., Bluetooth, near fieldcommunication (NFC), etc.). In such embodiments, the network-sideinterface 1602 comprises one or more antenna/radiating elements. Forexample, the network-side interface 1602 may include a single antenna,multiple separate antennas, or a multi-antenna array configured formulti-layer communication, e.g., single input multiple output (SIMO),multiple input single output (MISO), multiple input multiple output(MIMO), etc. In other embodiments, the transceiver 1600 transmits andreceives signaling over a wireline medium, e.g., twisted-pair cable,coaxial cable, optical fiber, etc. Specific processing systems and/ortransceivers may utilize all of the components shown, or only a subsetof the components, and levels of integration may vary from device todevice.

Referring now to FIG. 17, shown are examples of two very simplifiedsub-frame structures 1750, 1752 for grant-free transmission. For theseexamples, the horizontal direction is time and the vertical direction isfrequency. In both examples, there are pilot symbols 1754 that arepositioned to precede the bulk of the data within the sub-frame. In thefirst example 1750, all pilot symbols 1754 are transmitted during afirst OFDM symbol. In the second example 1752, there are pilot symbols1754 in the first OFDM symbol, and additional pilot symbols elsewherewithin the sub-frame. More generally, in some embodiments, the pilotsymbols used for activity detection are near the start of the framestructure. The exact location does not need to be the first symbol. Insome embodiments, several symbols near the start of the frame structureinclude pilot symbols. However, as noted previously, some embodimentsmay rely on pilot symbols located elsewhere than at the start of thesub-frame.

Referring to FIG. 18A, shown is a first example of a frame structureconfigured for the co-existence of grant-free and grant-based traffic,for example URLL and eMBB, provided by an embodiment of the invention.The vertical dimension is frequency, and the horizontal axis is time,showing a division into OFDM symbols. The first OFDM symbol is labelled1815. A system bandwidth is divided into two frequency partitions 1800,1802. The first partition 1800 is available for grant-free traffic andgrant-based traffic, with the possibility of overlap, as detailed below.The second partition 1802 is only available for grant-based traffic. Forgrant-based traffic, shown is a single TTI 1813 having a durationsuitable for grant-based traffic, for example having a 0.5 ms TTIduration. The TTI 1813 for grant-based traffic (“grant-based TTI”) issub-divided into four (more generally some two or more) sub-TTIs 1805,1807, 1809, 1811, each of which corresponds to a TTI for grant-freetraffic (“grant-free TTI”). Each of the four grant-free TTIs 1805, 1807,1809, 1811 has a duration suitable for grant-free traffic, 0.125 ms inthe illustrated example. The shorter TTI duration used in the firstfrequency partition is suitable for grant-free traffic requiring lowlatency.

For this embodiment and the other embodiments described herein, the TTIsize for grant-free traffic, the TTI size for grant-free traffic, thesize of the frequency partitions, the number of grant-free TTIs in agrant-based TTI, the number and location of pilots for grant-free andgrant-based traffic, the size and shape of resource areas and regions,can be defined on an implementation specific basis.

As noted above, the first partition 1800 is available for use bygrant-free traffic. Within the first partition 1800 there are fourresource areas 1806, 1808, 1810, 1812 within which grant-free sub-framescan be transmitted during the four grant-free TTIs 1805, 1807, 1809,1811. Given that grant-free transmission is unscheduled, in general, fora given instance of the frame structure of FIG. 18A, there may or maynot be any grant-free transmissions occupying these resources. In theexample of FIG. 18A, a new grant-free transmission occurs in resourcearea 1806, and first, second and third grant-free retransmissions occurin grant-free resource areas 1808, 1810, 1812 respectively. Each of thegrant-free transmissions includes pilot symbols at the start of thegrant-free sub-frames, as discussed previously with reference to FIG.17. For example, a grant-free sub-frame transmitted in resource area1806 contains pilot symbols 1842, 1844 in the first OFDM symbol.

Turning now to grant-based traffic, both partitions 1800, 1802 areavailable for grant-based traffic. Partition 1802 is available for usefree from any overlap with grant-free traffic, whereas grant-basedtraffic sent in partition 1800 is subject to possible overlap withgrant-free traffic. When full utilization is employed, the entirety ofboth partitions 1800, 1802 is used for grant-based traffic. When partialutilization is employed, the entirety of partition 1802 and a sub-set ofthe resources within partition 1800 are used for grant-based traffic.Grant-based UEs receive and process a downlink feedback channel 185o andbase their utilization of partition 1800 on the received feedback.

The downlink feedback channel 185o is used for transmitting theabove-discussed notification of activity detection. In the illustratedexample, the downlink feedback channel includes a respective feedbackopportunity 1854, 1856, during each sub-TTI 1807, 1809. The feedbackchannel 1850 is used to inform grant-based UEs of the existence ofgrant-free traffic in an area of possible overlap between grant-free andgrant-based traffic so that they can adjust grant-based transmission.The downlink feedback channel is incorporated into downlinktransmissions to notify grant-based UEs of which resources need to beclear of grant-based traffic in the shared partition 1800. As a specificexample, a set of downlink symbols are transmitted during a period ofpossible overlap between grant-free uplink traffic and grant-baseduplink traffic, and a few tones in one of the set of downlink symbols,for example the third downlink symbol in the set, is reserved foropportunistic feedback. The location of this feedback control signal maybe configurable.

The feedback opportunity 1854 can be used to adjust grant-basedtransmission in resource area 1810 during sub-TTI 1809, and the feedbackopportunity 1856 can be used to adjust grant-based transmission inresource area 1812 in sub-TTI 1811. For the illustrated example, thereis no feedback during sub-TTI 1805 because it cannot be generatedquickly enough following activity detection during the same sub-TTI.However, if it could be generated quickly enough, then feedback could beused to adjust grant-based transmission in sub-TTI 1807. There is nofeedback during sub-TTI 1811 as there are no further retransmissionsafter that sub-TTI.

In some embodiments, the downlink feedback is a broadcast signal forreception by multiple grant-based UEs. This is appropriate forsituations where multiple grant-based UEs may experience an overlap withgrant-free transmissions.

In some embodiments, the downlink feedback is unicast to a specificgrant-based UE. This can be pre-configured to indicate a particularco-existence scenario. This feedback may be different for differentgrant-based UEs. For example, the breakdown between grant-based vs.grant-free traffic can be different in different bands for differentgrant-based UEs.

In some embodiments, the downlink feedback is sent by puncturingdownlink data. Alternatively, dedicated resources can be employed forthe downlink feedback.

In some embodiments, the feedback is sent on an on demand basis, onlywhen necessary to indicate grant-free transmission in the overlapregion. On the receiver side, the feedback signal needs to be monitoredon an ongoing basis.

In the illustrated example, there is a grant-free transmission insub-frame 1806. The feedback opportunity 1854 in the second sub-TTI 1807is used to notify grant-based UEs of the existence of the grant-freetransmission. Based on each grant-free UE being configured to transmit anew transmission and three retransmissions in this example, thenotification is equivalently an indication of the existence ofretransmissions in resource areas 1810, 1812. In response, thegrant-based UEs do not transmit within resource areas 1810, 1812. Theoverall result is that grant-based traffic is present in partition 1802and is also present in resource areas 1806, 1808 within partition 1800.A single grant-based transport block may be transmitted in partitions1800, 1802, and/or different grant-based transport blocks may betransmitted in each of partitions 1800, 1802. In some embodiments, theentire structure of FIG. 18A can be considered a single grant-basedtransport block. Resource areas 1810, 1812 are punctured from thegrant-based perspective, meaning that grant-based traffic is nottransmitted using those resources. It can be seen that grant-basedtraffic transmitted in resource areas 1806, 1808 overlaps with theinitial grant-free transmission and first grant-free retransmission, butthat as a result of the notification, there is no overlap in resourceareas 1810, 1812. As such, the second and third retransmissions are notsubject to interference from the grant-based traffic.

Alternatively, the resources available for grant-based transmission canbe viewed as including the resources within partition 1802, and any ofthe resource areas 1806, 1808, 1810, 1812 in respect of which feedbackindicating an overlap has not been received.

In a specific example, partition 1800 includes 10 resource blocks, andpartition 1802 includes 50 resource blocks. When feedback is receivedindicating overlap, the 10 resource blocks in partition 1800 are notused during a subsequent TTI.

In some embodiments, the two partitions 1800, 1802 are in respectivesub-bands having different sub-carrier spacings. An example of this isdepicted in FIG. 1813 where the first frequency partition 1800 operateswithin a sub-band 1801 with a numerology having a 60 kHz sub-carrierspacing, whereas the second frequency partition 1802 operates within asub-band 1803 with a numerology having a 15 kHz sub-carrier spacing. Insome embodiments, a grant-based UE transmitting in the 60 kHz band isscheduled separately from a grant-based UE transmitting in the 15 kHzband. In another example, all traffic including grant-based andgrant-free traffic uses a 30 kHz sub-carrier spacing. In anotherexample, grant-free traffic uses a 30 kHz sub-carrier spacing andgrant-based traffic uses a 15 kHz sub-carrier spacing. In anotherexample, grant-free traffic uses a 60 kHz sub-carrier spacing andgrant-free traffic uses a 30 kHz sub-carrier spacing. In anotherexample, both grant-free and grant-based traffic may use a commonsub-carrier spacing, such as 60 kHz or 120 kHz, with different TTIdurations.

In some embodiments, the partitions 1800, 1802 are within a singlesub-band. An example is depicted in FIG. 18C where two frequencypartitions 1800, 1802 are within a single band 1820 with a 15 kHzsub-carrier spacing. Unlike the FIG. 18A example, in the FIG. 1813example, the grant-free partition 1800 and grant-based partition 1801employ the same numerology, however their TTI durations can still bedifferent as detailed above. This embodiment is particularly suitablefor the case where a transport block for a single UE is scheduled overboth partitions 1800 and 1802.

As detailed above, pilot symbols may be included at an early portion ofthe grant-free sub-frame structure. If a short TTI is employed, thechannel may not change much, and pilot symbols at the beginning of theTTI are sufficient for channel estimation as per the example of FIG. 17.Activity detection may be performed based on the pilot symbols at thebeginning of the TTI, or may also be based on later pilot symbols asdescribed previously. Effective grant-free SINR for a TTI can bereliably estimated using pilot signals placed at the beginning of theTTI because time fading is minimal within a short TTI

In some embodiments, the pilot sequences are sufficient to identify thenumber and identity of active grant-free UEs. In some embodiments, wherethe grant-free UE can be uniquely identified, and where specificresources assigned to retransmissions by that grant-free UE can bedetermined, the feedback instructs the grant-based UE to puncture onlythe specific resources occupied by the active grant-free UE. Examplesare provided below. This approach can be applied to any of theembodiments described herein.

In other embodiments, the pilot sequences are not uniquely assigned togrant-free UEs. In this case, the pilot sequences can still be used toestimate the number of active grant-free UEs, although an exactdetermination may not be possible. In such embodiments, partition 1800over the entire grant-free TTI can be punctured (e.g. all of region1810, 1812) (i.e., not used for grant-based traffic) when a number ofactive grant-free UEs is greater than a threshold, or when a predictednumber of retransmissions in a grant-free TTI is greater than athreshold.

In some embodiments, to enhance activity detection reliability,grant-free UEs may use autonomous power boost on pilot symbols so thatif they collide with grant-based data, they can still be reliablyestimated. Alternatively, grant-free pilot symbols may be exempted fromoverlap with grant-free traffic.

In some embodiments, grant-based pilot symbols and grant-free pilotsymbols are configured such that the grant-free pilot symbols do notoverlap with grant-based pilot symbols. Referring again to FIG. 18A,grant-based pilot symbols are indicated at 1860, and it can be seen thatthere is no overlap between the grant-based pilot symbols 1860 and thegrant-free pilot symbols 1840. The number of grant-based pilot symbols1860 in this and other embodiments is implementation specific. A longergrant-based TTI would benefit from more pilot symbols. More generally,grant-free pilot symbols and grant-based pilot symbols can also bemapped to any set of OFDM symbols, and may overlap.

In the described embodiments, grant-based pilot symbols are mapped tospecific OFDM symbols. Note that it is not necessarily the case thatentire OFDM symbols are mapped to by pilot symbols. The pilot symbolsmay be multiplexed with data in one or more OFDM symbols. More generallystill, for this embodiment and the other embodiments described herein,grant-based pilot symbol location can be arbitrary, can be scattered,can overlap with grant-free pilot symbols or traffic, can be confined toone or more OFDM symbols per scheduling interval etc. In the describedembodiments, grant-based pilot symbols are mapped to specific OFDMsymbols.

FIG. 18A shows resource areas for initial transmissions and specificgrant-free retransmissions. In other embodiments described below,resource areas are for initial transmission and grant-freeretransmissions, generally, and in other embodiments resource areas arenot dedicated to initial transmissions as opposed to retransmissions.For any of the embodiments described herein, the actual size of theseresource areas can be arbitrary. In a specific example, a resource areafor new transmissions may be larger than a region for firstretransmissions, and a resource area for first retransmissions may belarger than a resource area for second retransmissions.

In some embodiments, grant-based pilot symbols and grant-free pilotsymbols are configured such that the grant-free pilot symbols mayoverlap with grant-based pilot symbols. If overlap is permitted, acovariance matrix of grant-free and grant-based pilot sequence can befurther exploited to estimate the SINR of grant-free traffic.

In some embodiments, the timing of new grant-free transmissions isaligned as between all grant-free UEs. Referring to FIG. 18A, agrant-based TTI 1813 is aligned with four grant-free TTIs 1805, 1807,1809, 1811. All new grant-free transmissions occur in the first TTI1805. Re-transmissions occur in the subsequent TTIs 1807, 1809, 1811.Such a system simplifies activity detection, because a base station canidentify whether a transmission is a new transmission or aretransmission based on the TTI in which it occurs. In addition, theentirety of partitions 1800 and 1802 can be used for grant-based trafficwhen there is no grant-free transmission. However, a disadvantage is theincreased latency due to the fact that initial transmissions must waitfor the start of a longer grant-based TTI.

In some embodiments, the resources used by grant-free UEs follow acertain mapping, known to both the UEs and the base station when theytransmit new transmissions or retransmissions. An example is shown inFIG. 18D which shows a mapping to resource areas 1900, 1902, 1904 duringgrant-free TTIs 1901, 1903, 1905 for new transmissions, firstretransmissions and second retransmissions. Each resource area has 16resource blocks. The resource blocks of each resource area are dividedinto four regions each containing four resource blocks. Four resourceblocks is the unit of resource assigned for each UE if it has data totransmit for this example. This allocation may be based on averagepayload requirement and may be updated. The regions for TTI 1901 areindicated at 1912, 1914, 1916, 1918. Each region supports up to fourgrant-free UEs in this example. A list of four numbers depicted for eachregion represents a set of four UEs mapped to that region. A UE willmake grant-free transmissions using the regions to which it is mapped ina given TTI, if it has data to send. However, the UE may or may not havea transmission to make in a given region to which it is mapped. In theillustrated example, for initial transmissions, during TTI 1901, UEs 1,2, 3, 4 are mapped to region 1912; UEs 5, 6, 7, 8 are mapped to region1914; UEs 9, 10, 11, 12 are mapped to region 1916; and UEs 13, 14, 15,16 are mapped to region 1918. From one TTI to the next, the mappingchanges. For first retransmissions, during TTI 1903, UEs 1, 5, 9, 13 aremapped to region 1920; UEs 2, 6, 10, 14 are mapped to region 1922; UEs3, 7, 11, 15 are mapped to resource area 1924; and UEs 4, 8, 12, 16 aremapped to region 1926. For second retransmissions, during TTI 1905, UEs1, 10, 7, 18 are mapped to region 1930; UEs 5, 14, 4, 11 are mapped toregion 1932; UEs 9, 2, 8, 15 are mapped to resource area 1934; and UEs13, 6, 3, 12 are mapped to region 1936.

In some embodiments, where the base station can determine which UE isdetected (for example using the pilot sequence based approach referredto below), based on knowledge of a mapping such as that described withreference to FIG. 18D, the base station knows precisely the resourcesrequired by that UE for its second retransmission. In that case, thebase station can instruct grant-based UEs to only puncture thoseresources. For the example of FIG. 18D, if UE 1 is detected in region1912, feedback is sent on the downlink during TTI 1903, and grant-freeUEs are instructed to puncture uplink transmissions in region 1930 whichis where UE 1 is expected to make its second retransmission. Thismapping approach can be applied to any of the embodiments describedherein, including the TDD embodiments described below with reference toFIGS. 21A, 21B and 22, and does not require the specific mapping of FIG.18D.

Referring now to FIG. 18E, shown is another example of mapping of UEs toresource areas. The mapping of UEs to three resource areas is the sameas the mapping of UEs to resource areas 1900, 1902, 1904 described withreference to FIG. 18D, and as such the mapping will not be describedagain in detail. However, for this embodiment, there is no restrictionon when a first grant-free transmission is made as opposed to a first orsecond retransmission. Thus UE 1, for example, can make an initialtransmission in any of regions 1912, 1920, 1930. A specific example isdepicted in which initial transmissions for UEs 1 and 4 are representedby circled numbers, first retransmissions for UEs 1 and 4 arerepresented by numbers with squares around them, and secondretransmissions for UEs 1 and 4 are represented by numbers with diamondsaround them. With this embodiment, the base station detects newtransmissions from UEs 1 and 4 in region 1912 (for example using thepilot sequence based approach described below), and instructsgrant-based UEs to puncture the regions 1930, 1932 containing the secondretransmissions for UEs 1 and 4. More generally, a distinction can bemade between detected activity in respect of which there are enoughretransmissions remaining for feedback to be useful, and detectedactivity in respect of which there are not enough retransmissionsremaining for feedback to be useful. This can be done using the pilotsequence based approach, for example. This approach can also be appliedin embodiments in which resource areas are defined for initialretransmissions, and retransmissions generally (for example theembodiment of FIG. 20 described below).

In some embodiments, rather than requiring initial grant-freetransmissions to be aligned, a logical division of a bandwidth availablefor grant-free transmission is made between portions available for newtransmissions, and those available for retransmissions. A first exampleis depicted in FIG. 19A, which shows a specific logical division withinthe overlap partition 1800. Elements that are in common with FIGS.18A-18C are commonly numbered. This logical division may besemi-statically configured.

During the first grant-free TTI 1805 in FIG. 19A, the partition 1800 isdivided into a resource area 2000 for new transmissions, a resource area2002 for first retransmissions, and a resource area 2006 for secondretransmissions. During the second grant-free TTI 1807, the partition1800 is divided into a resource area 2008 for initial transmissions, aresource area 2010 for second retransmissions, and a resource area 2012for new retransmissions. During the third grant-free TTI 1809, thepartition 1800 is divided into a resource area 2014 for secondtransmissions, a resource area 2016 for new transmissions, and aresource area 2018 for first retransmissions. During the fourthgrant-free TTI 1811, the partition 1800 is divided into a resource area2020 for new transmissions, a resource area 2022 for firstretransmissions, and a resource area 2024 for second retransmissions.With this approach, a grant-free UE can make an initial transmission inany of the four grant-free TTIs. Each resource area for newtransmissions has a corresponding area for first retransmissions and acorresponding area for second retransmissions. For example, resourcearea 2000 for first retransmissions has a corresponding area 2008 forfirst retransmission and a corresponding area 2014 for secondretransmissions.

After an initial transmission is made in a resource area reserved forfirst transmissions, retransmissions are sent in the correspondingresource areas for retransmissions. In the example of FIG. 19A, eachgrant-free UE makes two retransmissions, but a similar approach can beused for another number of retransmissions. For example, a grant-free UEthat makes an initial transmission using resource area 2000 makes itsfirst and second retransmissions using resource areas 2008 and 2014.

With this embodiment, the pilot symbols of the first grant-freetransmissions are used by the base station for activity detection andoptionally to assess channel quality, for the grant-free transmission.If activity is detected, or if activity is detected and channel qualityis poor in respect of a new transmission made in one of the resourceareas reserved for new transmissions (as defined by some threshold orcriterion) then the downlink feedback channel is used to indicate thatthe corresponding resource area reserved for second retransmissionsshould be cleared of grant-based traffic. For example, if a newtransmission occurs in resource area 2000 for which channel quality isdetermined to be poor, feedback is sent using feedback opportunity 1854which indicates resource area 2014 should be clear of grant-basedtraffic. In the illustrated example, feedback is also used to indicatethat resource area 2024 should be clear of grant-based traffic. In someembodiments, the first retransmission area is also or alternativelycleared of grant-based traffic if feedback can be generated andreceived/processed quickly enough This embodiment includes the optionalfeature of only generating the downlink feedback where the channelquality is poor, for example when the SINR is below a threshold. Thisfeature can be added to any of the embodiments described herein relatingto controlling the transmissions by grant-based UEs.

FIG. 19B shows an example of a mapping of UEs to the resource areas2000, 2002, 2004 of FIG. 19A. Such a mapping can be defined for any setof resource areas. The mapping can be different for different resourceareas, and/or for different TTIs. In some embodiments, new transmissionsand retransmissions are mapped differently to avoid repeated collisions.The mapping is the same as the mapping of UEs to resource areas 1900,1902, 1904 described with reference to FIG. 19D, so it will not bedescribed again in detail.

In some embodiments, all grant-free UEs are configured to make the samenumber of retransmissions. Alternatively, differing numbers ofretransmissions can be configured for different UEs. For example, someUEs may be configured with one retransmission, and other UEs may beconfigured with two retransmissions. The frequency of activity by UEs ofdifferent categories of UEs may differ significantly. For example, theremay be more activity among UEs that transmit one retransmission comparedto UEs that transmit two retransmissions. This could have the effect ofsome retransmission regions being underutilized. In some embodiments,resource areas are not dedicated specifically to be a certainretransmission (e.g. first or second), but rather some resource areasare dedicated to new transmissions, and other resources are dedicated toretransmissions of any type. Having such common retransmission resourceareas may yield improved resource utilization. In some embodiments,based on pilot sequences, using for example an approach detailed below,the base station can determine which category of UE a given UE belongsto, for example a category with one retransmission as opposed to acategory with two retransmissions. This information can be used by thebase station to cause the appropriate region to be punctured bygrant-based UEs.

An example of this approach is depicted in FIG. 20. During the firstgrant-free TTI 1805, the partition 1800 is divided into a resource area2100 for new transmissions, and a resource area 2102 for retransmissionsgenerally. The resource area 2102 for retransmissions and the other suchresource areas may be utilized for a grant-free UE to transmit a firstretransmission or a second retransmission (more generally still anyretransmission). During the second grant-free TTI 1807, the partition1800 is divided into a resource area that includes areas 2104 forretransmissions, and a resource area 2108 for new transmissions. Duringthe third grant-free TTI 1809, the partition 1800 is divided into aresource area 2110 for new transmissions, and a resource area 2112 forretransmissions. During the fourth grant-free TTI 1811, the partition1800 is divided into a resource area 2114 for retransmissions, aresource area 2116 for new transmissions. With this approach, a UE canmake an initial transmission in any of the four grant-free TTIs. Afteran initial transmission is made, retransmissions are sent in theresource areas reserved for retransmissions in subsequent grant-freeTTIs. In the illustrated example, feedback is used to indicate that apart of resource area 2104 and resource area 2112 should be clear ofgrant-based traffic. In this example, a determination has been made thata retransmission will occur in a specific part of resource area 2104,and only that specific part of resource area 2104 is punctured. Amapping such as described by way of example with reference to FIG. 19Bcan be defined for embodiments that take the approach of FIG. 20.

As noted above, in some embodiments, the grant-free pilot symbols areused to distinguish between a initial transmission and a specificretransmission and/or to distinguish between different categories of UEsin terms of number of retransmissions expected. For a given UE, a firstgrant-free pilot symbol (or a pilot symbol from a first pool of pilotsymbols) is used with an initial transmission, and a second grant-freepilot symbol (or a pilot symbol from a second pool of pilot symbols) isused with a retransmission or a specific retransmission. See, forexample, commonly assigned U.S. application Ser. No. 15/088,607 filedApr. 1, 2016, entitled “System and Method for Pilot Assisted Grant-freeUplink Transmission Identification”, hereby incorporated by reference inits entirety. In some embodiments, this information is used to moreprecisely determine the resource used for the grant-free transmissionsuch that only that precise resource need be punctured from thegrant-based perspective.

Grant-free self-contained TDD frame structure

In another embodiment, an activity based feedback mechanism is employedin respect of transmissions by grant-free UEs that employ aself-contained time division duplex (TDD) frame structure. An example isdepicted in FIG. 21A which shows a grant-free sub-frame 2200 having adownlink segment 2203, a guard period 2204, and an uplink segment 2206.Such a sub-frame structure might, for example, be based on a 60 kHzsub-carrier spacing with 0.1 to 0.2 ms duration. If there are K symbolsin the uplink segment, a base station can detect activity and estimateSINR thresholds for a subset N<<K symbols. N could be as low as N=1. Inthe illustrated example, the base station detects activity during twosymbols where pilot symbols are mapped (the first 2210 and seventh2212). The base station can then send feedback in the downlink segment2214 of the next sub-frame 2216.

In another embodiment, the uplink segment precedes the downlink segment,and the feedback may be sent in the downlink segment in the samesub-frame. An example is depicted in FIG. 21B, in which measurementstake place during uplink segment 2240 on symbols 2250, 2252, andfeedback is sent during downlink segment 2242 of the same sub-frame.

In some embodiments, the feedback described is received by thegrant-free UE that made the transmission, and can be used by thegrant-free UE to reduce its retransmission by sending fewer than itsdefault number of retransmissions. For example, if the base stationdetects the grant-free UE, and detects an SINR that is greater than athreshold and/or low activity/collision among grant-free UEs, the basestation sends the feedback, and the grant-free UE may be configured tonot retransmit, or to make a reduced number of retransmissions. Thefeedback functions as a pseudo-acknowledgement. It is not a fullacknowledgement because it is not based on successfully decoding ofreceived data, but rather is based on a channel quality measurement.This threshold based approach can be applied to any of the embodimentsdescribed herein to reduce retransmission by grant-free UEs.

It may be possible that some grant-free UEs experience a very goodchannel, and a very low error rate, e.g. <1×10⁻⁶ is predicted based onmeasurement. In such a case, the base station can use the feedback toprovide the pseudo acknowledgement to the UEs indicating that they donot need to retransmit. Alternatively, or in addition, the base stationcan use the feedback to provide the pseudo acknowledgement to the UEsindicating they can stop retransmitting.

Another example is depicted in FIG. 22, which builds upon the example ofFIG. 21, and employs common reference numerals. Example transmissions ofUEs numbered 1 to 12 are depicted. Initial transmissions are representedby circled numbers, first retransmissions are represented by numberswith squares around them, and second retransmissions are represented bynumbers with diamonds around them. With the example of FIG. 22, forframe 2200 there is a dedicated sub-band 2301 for initial transmissions,and a dedicated sub-band 2303 for retransmissions. In frame 2202 thereare dedicated sub-bands 2305, 2307 for retransmissions and newtransmissions respectively. It is noted that the resource areadefinitions and mappings described previously for example with referenceto FIGS. 19A-19E, 20A, 20B, and 21 and generalizations thereof, and theuse of feedback to adjust grant-based UE transmission can similarly beapplied in a TDD context.

In the illustrated example, the base station gauges channel quality forthe 12 UEs during the pilot period 2210, and sends feedback during thefollowing downlink period 2214 For this example, the base station hasprovided feedback to some UEs instructing them to retransmit fewer thantheir preconfigured number of retransmissions. In the illustratedexample, during the first sub-frame 2200, UEs 1, 2, 3 and 4 make initialtransmissions. Feedback is sent during downlink portion 2214 of thesecond sub-frame to UEs 1 and 3 indicating not to retransmit. As such,UEs 1 and 3 can use the next frame 2202 for initial transmissions ofadditional data if desired. During the first sub-frame 2200, UEs 6, 8, 9and 12 are making first retransmissions, and UEs 5, 7, 10, 13, 14 aremaking second retransmissions. Feedback is sent during downlink portion2214 of the second sub-frame 2202 indicating that UEs 6 and 8 are tostop retransmitting. The result is that of the UEs 6, 8, 9 and 12 thatmade a first retransmission, only UEs 9 and 12 make secondretransmissions in the second sub-frame 2202. The next frame 2202 can beused for initial transmissions for UEs 6 and 8 if they have more data tosend.

It is noted that while this approach of reducing/eliminatingretransmissions is described in the context of the TDD examples of FIGS.21A and 21B, and 22, the same approach can be used in the otherembodiments described herein, in addition to, or instead of, using thefeedback to control grant-free transmission.

In some embodiments, for robustness, the downlink control information istransmitted using resources dedicated to the control channel and notused for other purposes. In some embodiments, grant-free and grant-basedtraffic may share the downlink control resources in a TDM/FDM fashion.

Feedback message

As detailed above, the grant-free partition may consist of severalresource areas where UEs are mapped. The feedback message may be afunction of the number of resource areas, and whether the feedbackconcerns a new transmission or a re-transmission. For example, in oneembodiment, the feedback message has two fields. The first field denoteswhether the feedback concerns new transmissions or retransmissions, andthe second field is a bitmap of the resource areas. More detailedfeedback is also possible, depending on UE capability.

In many of the embodiments described, the feedback is used to indicatewhen grant-based UEs are to stop transmitting in an area of overlap. Inanother embodiment, grant-based traffic can be scheduled based on thefeedback to avoid or mitigate collisions with grant-freeretransmissions.

Referring now to FIG. 23A, shown is a simplified diagram of part a basestation that can operate using multiple numerologies. In this example,there are L supported numerologies, where L>=2, each numerologyoperating over a respective sub-band with a respective sub-carrierspacing. However, the approaches described herein can also be appliedwhen there is only a single numerology.

For each numerology, there is a respective transmit chain 2400, 2402.FIG. 23A shows simplified functionality for the first and Lthnumerology; the functionality for other numerologies would be similar.Also shown in FIG. 23B is simplified functionality for a receive chain2403 for a receiver operating using the first numerology.

The transmit chain 2400 for the first numerology includes aconstellation mapper 2410, subcarrier mapping and grouping block 2411,IFFT 2412 with subcarrier spacing SC₁, pilot symbol and cyclic prefixinsertion 2414, and frequency localization operator 2416 (for examplefiltering, sub-band filtering, windowing, sub-band windowing). Alsoshown is a scheduler 2400 that performs scheduling. It is noted thatdepending on the frequency localization operator implementation,different guard zones may be needed at the two edges of the spectrumand/or between sub-bands with different numerologies (i.e. differentsub-carrier spacings). In some embodiments, the guard zones aredetermined taking into account frequency localization capabilities ofboth the transmitter and receiver. Also shown is a feedback generator2454.

In operation, constellation mapper 2410 receives UE data (moregenerally, UE content containing data and/or signalling) for K₁ UEs,where K₁>=1. The constellation mapper 2410 maps the UE data for each ofthe K₁ UEs to a respective stream of constellation symbols and outputsthis at 2420. The number of UE bits per symbol depends on the particularconstellation employed by the constellation mapper 2410. In the exampleof quadrature amplitude modulation (QAM), 2 bits from for each UE aremapped to a respective QAM symbol.

For each OFDM symbol period, the subcarrier mapping and grouping block2411 groups and maps the constellation symbols produced by theconstellation mapper 2410 to up to P inputs of the IFFT 2412 at 2422.The grouping and mapping is performed based on scheduler information,which in turn is based on channelization and resource block assignment,in accordance with a defined resource block definition and allocationfor the content of the K₁ UEs being processed in transmit chain 2400. Pis the size of the IFFT 2412. Not all of the P inputs are necessarilyused for each OFDM symbol period. The IFFT 2412 receives up to Psymbols, and outputs P time domain samples at 2424. Following this, insome implementations, time domain pilot symbols are inserted and acyclic prefix is added in block 2414. The frequency localizationoperator 2416 may, for example, apply a filter f₁(n) which limits thespectrum at the output of the transmit chain 2400 to preventinterference with the outputs of other transmit chains such as transmitchain 2402. The frequency localization operator 2416 also performsshifting of each sub-band to its assigned frequency location.

The functionality of the other transmit chains, such as transmit chain2402 is similar. The outputs of all of the transmit chains are combinedin a combiner 2404 before transmission on the channel.

The activity detector 2452 performs activity detection and/or SINRmeasurement to detect and measure the signal quality of uplinktransmissions from grant-free UEs. The feedback generator 2454 generatesfeedback based on an output of activity detector 2452 (described belowas part of the transmit chain) in accordance with one of the methodsdescribed herein. This can be transmitted by puncturing user data at theinput to the constellation mappers, or on a dedicated downlink feedbackchannel.

FIG. 23B shows a simplified block diagram of a receive chain for of abase station receiving using a first numerology depicted at 2403. Thisfunctionality would be replicated where multiple numerologies aresupported. The receive chain 2403 includes frequency localizationoperator 2430, cyclic prefix deletion and pilot symbol processing 2432,fast Fourier transform (FFT) 2434, subcarrier de-mapping 2436 andequalizer 2438. Each element in the receive chain performs correspondingreverse operations to those performed in the transmit chain. Also shownis activity detector 2452 that performs activity detection using any oneof the methods described herein. The output of the activity detector2452 is passed to the feedback generator 2454.

The transmit chain of a grant-free UE and a grant-based UE may besimilar to that of a base station although there would be no schedulerand no feedback generator 2452. Also, for a grant-free UE typically asingle numerology is supported; a grant-based UE may support one ormultiple numerologies

The receive chain of a grant-free UE and a grant-based UE may be similarto that of a base station although again for a grant-free UE typically asingle numerology is supported; a grant-based UE may support one ormultiple numerologies. In place of the activity detector 2452, agrant-free UE may have a feedback processor that processes receivedfeedback and modifies retransmission behaviour using of the methodsdetailed previously. Alternatively, or in addition, a grant-based UE mayhave a feedback processor that processes received feedback and modifiesits transmissions using one of the methods detailed previously.

Although the description has been described in detail, it should beunderstood that various changes, substitutions and alterations can bemade without departing from the spirit and scope of this disclosure asdefined by the appended claims. Moreover, the scope of the disclosure isnot intended to be limited to the particular embodiments describedherein, as one of ordinary skill in the art will readily appreciate fromthis disclosure that processes, machines, manufacture, compositions ofmatter, means, methods, or steps, presently existing or later to bedeveloped, may perform substantially the same function or achievesubstantially the same result as the corresponding embodiments describedherein. Accordingly, the appended claims are intended to include withintheir scope such processes, machines, manufacture, compositions ofmatter, means, methods, or steps.

The following references are related to subject matter of the presentapplication. Each of these references is incorporated herein byreference in its entirety: U.S. patent application Ser. No. 15/142,638filed on Apr. 29, 2016.

Embodiments of this application describe, support, and enable thefollowing claims: 1. A method for mitigating interference, the methodcomprising: detecting, by a base station, a grant-free uplinktransmission over a first uplink resource; determining, by the basestation, that a retransmission of the grant-free uplink transmissionwill occur over a second uplink resource, the second uplink resourcehaving been previously scheduled to carry a grant-based uplinktransmission from a user equipment (UE); and transmitting, by the basestation, a signal over a downlink resource, the signal instructing theUE to adjust a transmission parameter of the grant-based uplinktransmission. 2. The method of claim 1, wherein the retransmission ofthe grant-free uplink transmission over the second uplink resource is agrant-free transmission. 3. The method of any of claim 1 or 2, whereinthe retransmission of the grant-free uplink transmission over the seconduplink resources is a grant-based transmission that is scheduled overthe second uplink resource. 4. The method of any of claim 1, 2, or 3,wherein the grant-free uplink transmission is an original uplinktransmission. 5. The method of any of claims 1-4, wherein the firstuplink resource and the second uplink resource are time-domainresources. 6. The method of claim 5, wherein the first uplink resourceand the second uplink resource each include one or more orthogonalfrequency division multiplexed (OFDM) symbols. 7. The method of any ofclaims 1-6, wherein the signal instructs the UE to adjust thetransmission parameter of the grant-based uplink transmission byinstructing the UE to reduce a transmit power level of the grant-baseduplink transmission during the second uplink resource. 8. The method ofany of claims 1-7, wherein the signal instructs the UE to adjust thetransmission parameter of the grant-based uplink transmission byinstructing the UE to mute the grant-based uplink transmission duringthe second uplink resource. 9. The method of any of claims 1-8, whereinthe grant-based uplink transmission was previously scheduled to beperformed over a set of uplink resources that includes the second uplinkresource and one or more additional uplink resources, and wherein thesignal further instructs the UE to adjust the transmission parameter ofthe grant-based uplink transmission by instructing the UE to mute thegrant-based uplink transmission over the second uplink resource and toadapt a modulation and coding scheme (MCS) level used to transmitportions of the grant-based uplink transmission over the one or moreadditional uplink resources. 10. The method of any of claims 1-9,wherein the signal instructs the UE to adjust the transmission parameterof the grant-based uplink transmission by instructing the UE to shiftthe grant-based uplink transmission from the second uplink resource to athird uplink resource of the subframe. 11. The method of any of claims1-10, wherein the signal instructs the UE to adjust the transmissionparameter of the grant-based uplink transmission by instructing the UEto postpone the grant-based uplink transmission. 12. The method of claim11, wherein the signal instructs the UE to adjust the transmissionparameter of the grant-based uplink transmission by instructing the UEto postpone the grant-based uplink transmission until a subsequent grantis received. 13. The method of claim 11, wherein the signal instructsthe UE to adjust the transmission parameter of the grant-based uplinktransmission by instructing the UE to postpone the grant-based uplinktransmission. 14. The method of claim 13, wherein the signal instructsthe UE to postpone the grant-based uplink transmission until asubsequent subframe specified by the signal. 15. The method of any ofclaims 1-14, wherein detecting the grant-free uplink transmissioncomprises: detecting the presence of the grant-free uplink transmissionbased on a pilot symbol carried by the grant-free uplink transmission,wherein the signal is transmitted prior to the base station attemptingto decode at least some of the data carried by the grant-free uplinktransmission. 16. The method of any of claims 1-15, wherein determiningthat the retransmission of the grant-free uplink transmission will occurover the second uplink resource in the subframe comprises: detecting anidentifier in a pilot symbol carried by the grant-free uplinktransmission; and determining that the retransmission of the grant-freeuplink transmission will occur in the second uplink resource based on asemi-static resource configuration associated with the identifier. 17.The method of claim 16, wherein the semi-static resource configurationcomprises a resource hopping pattern. 18. The method of claim 16,wherein detecting the identifier in the pilot symbol carried by thegrant-free uplink transmission comprises detecting a UE-specificidentifier or a group-specific identifier in the pilot symbol carried bythe grant-free uplink transmission. 19. The method of claim 16, whereindetecting the identifier in the pilot symbol carried by the grant-freeuplink transmission comprises detecting an identifier in the pilotsymbol carried by the grant-free uplink transmission, the identifier inthe pilot symbol being associated with a time or frequency resourcehopping pattern. 20. The method of claim 16, wherein the signal istransmitted prior to the base station attempting to decode at least someof the data carried by the grant-free uplink transmission. 21. Themethod of claim 16, wherein the identifier is a UE-specific identifier.22. The method of any of claims 1-21, wherein the signal is sent in agroup specific region of a downlink frame. 23. The method of any ofclaims 1-23, wherein the signal is a broadcast control signal.

24. An apparatus comprising: a processor; and a non-transitory computerreadable storage medium storing programming for execution by theprocessor, the programming including instructions to: detect agrant-free uplink transmission over a first uplink resource of asubframe; determine that a retransmission of the grant-free uplinktransmission will occur over a second uplink resource in the subframe,the second uplink resource of the subframe having been previouslyscheduled to carry a grant-based uplink transmission from a userequipment (UE); and transmit a signal over a downlink resource of thesubframe, the signal instructing the UE to adjust a transmissionparameter of the grant-based uplink transmission.

25. A method for reconfiguring grant-free resources, the methodcomprising: scheduling, by a base station, a first uplink resource tocarry a grant-based uplink transmission of a first user equipment (UE),the first uplink resource being included in an initial set of uplinkresources available for grant-free uplink transmissions; andbroadcasting, by the base station, a control message that updates theset of uplink resources for grant-free uplink transmissions, the updatedset of uplink resources excluding the first uplink resource. 26. Themethod of claim 25, wherein the first uplink resource is one or moreorthogonal frequency division multiplexed (OFDM) symbols.

27. A method for mitigating interference in a subframe, the methodcomprising: receiving, by a first user equipment (UE), a schedulinginstruction from a base station, the scheduling instruction indicatingthat uplink resources are scheduled to carry a grant-based uplinktransmission of the first UE; monitoring, by the first UE, one or moredownlink resources outside a downlink control channel associated withthe first UE for an indication that a retransmission of a grant-freeuplink transmission is to occur over a subset of the uplink resourcesscheduled to carry the grant-based uplink transmission of the first UE;and puncturing, by the first UE, a portion of the grant-based uplinktransmission corresponding to the subset of uplink resources upondetecting the indication that the grant-free uplink transmission is tooccur over the subset of uplink resources. 28. The method of claim 27,wherein the grant-free uplink transmission is performed by a second UEthat is different than the first UE. 29. The method of claim 28, whereinthe indication that the retransmission of the grant-free uplinktransmission is to occur over the subset of uplink resources is detectedin a downlink control channel associated with the second UE. 30. Themethod of claim 28, wherein the indication that the retransmission ofthe grant-free uplink transmission is to occur over the subset of uplinkresources is detected in an acknowledgement or negative acknowledgmentchannel associated with the second UE. 31. The method of claim 28,wherein the indication that the retransmission of the grant-free uplinktransmission is to occur over the subset of uplink resources is detectedin one or more downlink data channel resources assigned to the secondUE. 32. The method of claim 28, wherein the indication that theretransmission of the grant-free uplink transmission is to occur overthe subset of uplink resources is detected in one or more downlink datachannel resources assigned to a third UE that is different than both thesecond UE and the first UE. 33. The method of claim 28, wherein theindication that the retransmission of the grant-free uplink transmissionis to occur over the subset of uplink resources is detected in adownlink control channel associated with a third UE that is differentthan both the second UE and the first UE. 34. The method of any ofclaims 27-33, further comprising: performing rate adaptation over one ormore remaining portions of the grant-based uplink transmission tocompensate for the punctured portion of the grant-based uplinktransmission.

35. A method for mitigating interference in a subframe, the methodcomprising: determining, by a base station, that a retransmission of agrant-free uplink transmission will occur over a subset of uplinkresources scheduled to carry a grant-based uplink transmission of afirst user equipment (UE); and transmitting, by the base station, anindication to the first UE, the indication prompting the first UE topuncture a portion of the grant-based uplink transmission thatcorresponds to the subset of uplink resources over which theretransmission of the grant-free transmission will occur. 36. The methodof claim 35, wherein the grant-free uplink transmission is performed bya second UE that is different than the first UE. 37. The method of claim36, wherein the indication is transmitted over a downlink controlchannel associated with the second UE.

What is claimed is:
 1. A method for mitigating interference, the methodcomprising: detecting, by a base station, a grant-free uplinktransmission over a first uplink resource; determining, by the basestation, that a retransmission of the grant-free uplink transmissionwill occur over a second uplink resource, the second uplink resourcehaving been previously scheduled to carry a grant-based uplinktransmission from a user equipment (UE); and transmitting, by the basestation, a signal over a downlink resource, the signal instructing theUE to adjust a transmission parameter of the grant-based uplinktransmission.
 2. The method of claim 5, wherein the first uplinkresource and the second uplink resource each include one or moreorthogonal frequency division multiplexed (OFDM) symbols.
 3. The methodof claim 1, wherein the signal instructs the UE to adjust thetransmission parameter of the grant-based uplink transmission byinstructing the UE to reduce a transmit power level of the grant-baseduplink transmission during the second uplink resource.
 4. The method ofclaim 1, wherein the signal instructs the UE to adjust the transmissionparameter of the grant-based uplink transmission by instructing the UEto mute the grant-based uplink transmission during the second uplinkresource.
 5. The method of claim 1, wherein the grant-based uplinktransmission was previously scheduled to be performed over a set ofuplink resources that includes the second uplink resource and one ormore additional uplink resources, and wherein the signal furtherinstructs the UE to adjust the transmission parameter of the grant-baseduplink transmission by instructing the UE to mute the grant-based uplinktransmission over the second uplink resource and to adapt a modulationand coding scheme (MCS) level used to transmit portions of thegrant-based uplink transmission over the one or more additional uplinkresources.
 6. The method of claim 1, wherein the signal instructs the UEto adjust the transmission parameter of the grant-based uplinktransmission by instructing the UE to shift the grant-based uplinktransmission from the second uplink resource to a third uplink resourceof the subframe.
 7. The method of claim 1, wherein the signal instructsthe UE to adjust the transmission parameter of the grant-based uplinktransmission by instructing the UE to postpone the grant-based uplinktransmission.
 8. The method of claim 7, wherein the signal instructs theUE to adjust the transmission parameter of the grant-based uplinktransmission by instructing the UE to postpone the grant-based uplinktransmission until a subsequent grant is received.
 9. The method ofclaim 7, wherein the signal instructs the UE to adjust the transmissionparameter of the grant-based uplink transmission by instructing the UEto postpone the grant-based uplink transmission.
 10. The method of claim9, wherein the signal instructs the UE to postpone the grant-baseduplink transmission until a subsequent subframe specified by the signal.11. The method of claim 1, wherein detecting the grant-free uplinktransmission comprises: detecting the presence of the grant-free uplinktransmission based on a pilot symbol carried by the grant-free uplinktransmission, wherein the signal is transmitted prior to the basestation attempting to decode at least some of the data carried by thegrant-free uplink transmission.
 12. The method of claim 1, whereindetermining that the retransmission of the grant-free uplinktransmission will occur over the second uplink resource in the subframecomprises: detecting an identifier in a pilot symbol carried by thegrant-free uplink transmission; and determining that the retransmissionof the grant-free uplink transmission will occur in the second uplinkresource based on a semi-static resource configuration associated withthe identifier.
 13. The method of claim 12, wherein detecting theidentifier in the pilot symbol carried by the grant-free uplinktransmission comprises detecting a UE-specific identifier or agroup-specific identifier in the pilot symbol carried by the grant-freeuplink transmission.
 14. The method of claim 12, wherein detecting theidentifier in the pilot symbol carried by the grant-free uplinktransmission comprises detecting an identifier in the pilot symbolcarried by the grant-free uplink transmission, the identifier in thepilot symbol being associated with a time or frequency resource hoppingpattern.
 15. The method of claim 12, wherein the signal is transmittedprior to the base station attempting to decode at least some of the datacarried by the grant-free uplink transmission.
 16. An apparatuscomprising: a processor; and a non-transitory computer readable storagemedium storing programming for execution by the processor, theprogramming including instructions to: detect a grant-free uplinktransmission over a first uplink resource of a subframe; determine thata retransmission of the grant-free uplink transmission will occur over asecond uplink resource in the subframe, the second uplink resource ofthe subframe having been previously scheduled to carry a grant-baseduplink transmission from a user equipment (UE); and transmit a signalover a downlink resource of the subframe, the signal instructing the UEto adjust a transmission parameter of the grant-based uplinktransmission.
 17. A method for reconfiguring grant-free resources, themethod comprising: scheduling, by a base station, a first uplinkresource to carry a grant-based uplink transmission of a first userequipment (UE), the first uplink resource being included in an initialset of uplink resources available for grant-free uplink transmissions;and broadcasting, by the base station, a control message that updatesthe set of uplink resources for grant-free uplink transmissions, theupdated set of uplink resources excluding the first uplink resource. 18.A method for mitigating interference in a subframe, the methodcomprising: receiving, by a first user equipment (UE), a schedulinginstruction from a base station, the scheduling instruction indicatingthat uplink resources are scheduled to carry a grant-based uplinktransmission of the first UE; monitoring, by the first UE, one or moredownlink resources outside a downlink control channel associated withthe first UE for an indication that a retransmission of a grant-freeuplink transmission is to occur over a subset of the uplink resourcesscheduled to carry the grant-based uplink transmission of the first UE;and puncturing, by the first UE, a portion of the grant-based uplinktransmission corresponding to the subset of uplink resources upondetecting the indication that the grant-free uplink transmission is tooccur over the subset of uplink resources.
 19. The method of claim 18,wherein the indication that the retransmission of the grant-free uplinktransmission is to occur over the subset of uplink resources is detectedin a downlink control channel associated with the second UE.
 20. Themethod of claim 18, wherein the indication that the retransmission ofthe grant-free uplink transmission is to occur over the subset of uplinkresources is detected in an acknowledgement or negative acknowledgmentchannel associated with the second UE.
 21. The method of claim 18,wherein the indication that the retransmission of the grant-free uplinktransmission is to occur over the subset of uplink resources is detectedin one or more downlink data channel resources assigned to the secondUE.
 22. The method of claim 18, wherein the indication that theretransmission of the grant-free uplink transmission is to occur overthe subset of uplink resources is detected in one or more downlink datachannel resources assigned to a third UE that is different than both thesecond UE and the first UE.
 23. The method of claim 18, wherein theindication that the retransmission of the grant-free uplink transmissionis to occur over the subset of uplink resources is detected in adownlink control channel associated with a third UE that is differentthan both the second UE and the first UE.
 24. The method of claim 18,further comprising: performing rate adaptation over one or moreremaining portions of the grant-based uplink transmission to compensatefor the punctured portion of the grant-based uplink transmission.
 25. Amethod for mitigating interference in a subframe, the method comprising:determining, by a base station, that a retransmission of a grant-freeuplink transmission will occur over a subset of uplink resourcesscheduled to carry a grant-based uplink transmission of a first userequipment (UE); and transmitting, by the base station, an indication tothe first UE, the indication prompting the first UE to puncture aportion of the grant-based uplink transmission that corresponds to thesubset of uplink resources over which the retransmission of thegrant-free transmission will occur.